user5000: Does samsara exist? Or does samsara not exists and it just looks to us that it exists, but in reality it is all the same "thing"?
Here's the updated question, to make it clearer:
UPDATE
Nibanna is the cessation of all that is conditioned, i.e. samsara.
As I understand it, when you attain Nibanna which is unconditioned, then you are out of samsara.
Does this mean, that when you attain Nibanna, samsara:

does not exist but it exists for other beings in samsara?
does not exist, and neither it exists for the other beings in samsara, because Nibanna is unconditioned, so there is no samsara, and consequently there are no beings?

Which one is it? 1 or 2?

user5513: When we wake up from dream, does it exist for others?

user-1: 
Samsara exists. 2. Samsara does not exist. 3. Samsara both exists and does not exist. 4. Samsara neither exists nor not exists. All of these statements are true. All of these statements are false. All of these statements are both true and false. All of these statements are neither true nor false.


user7090: Samsara exist because there is enlightenment- free from Samara.
Just like wealth exist because there are poor. 
Only if one is free from Samsara can one see Samsara. 
If everyone is in Samsara, then how can one see Samsara? 
That is what Buddha is here to teach 

user7525: Excerpt from "Lamp of Mahamudra" by Tsele Natsok Rangdrol:

"Section One - Ground Mahamudra"
"The View"
"Your natural essence cannot be established as either samsara or nirvana.  Not confined by any one extreme, free from the limitations of exaggeration or denigration, it is not tainted nor spoiled by such designations as pleasant or unpleasant, being or not being, existent or non-existent, permanent or annihilated, self or other, and so forth...
Yet, no matter how it manifests, ultimately this essence has no true existence...
It is the actual basis of all that appears and exists, the whole of samsara and nirvana.
When you realize its nature, knowing its real condition, you are called a Buddha.  When you do not realize it, remaining ignorant of it and experiencing confusion, you are called a sentient being."

For any who are interested, "Lamp of Mahamudra" and "The Heart of the Matter", both by Tsele Natsok Rangdrol, have been combined in a single book, entitled "Heart Lamp", translated by Erik Pema Kunsang, Rangjung Yeshe Publications, North Atlantic Books.

user471: From SN 15.3:

“Mendicants, transmigration (samsara) has no known beginning. No first point is
found of sentient beings roaming and transmigrating, hindered by
ignorance and fettered by craving. What do you think? Which is more:
the flow of tears you’ve shed while roaming and transmigrating for
such a very long time—weeping and wailing from being united with the
unloved and separated from the loved—or the water in the four oceans?”
“As we understand the Buddha’s teaching, the flow of tears we’ve shed
while roaming and transmigrating is more than the water in the four
oceans.”
“Good, good, mendicants!

Samsara exists and it has no beginning.
Who shed the tears for such a long time, that could exceed the four oceans?
It's the self. The mental idea of the self. It's the self that experiences samsara.
For whom does samsara exist? It exists for the self.
If there's no self at all, there's no samsara.
If there's self, there's samsara.
So, basically, samsara exists dependent on mind-body phenomena. So long as mind-body phenomena exists, so does samsara.

Also at the same time, samsara doesn't really exist. Why?
Sabbe dhamma anatta - all phenomena is not self.

user-1: If you use "exists" in the Buddhist context, you might be understood as "has own, unconditioned essence" which is the traditional use -- here, the object in question cannot suddenly become or unbecome according to circumstances, because it always "is". Or as "is real / refers to an actual experience" which is the more popular understanding. Not being explicit about how this word is being can be confusing.
Having said that, to the questions:

Does samsara exist? Or does samsara not exists and it just looks to us that it exists, but in reality it is all the same "thing"?

I'm understanding samsara here as a word to describe the cycle of birth and death. 
Whether it "exists" -- in the traditional sense -- or "not exists" is a philosophical topic whose answer might change according to the philosophy of each school (though I think no school who would declare existence of phenomena or concepts have survived).

Does this mean, that when you attain Nibanna, samsara does not exist but it exists for other beings in samsara?

from the following:
The Buddha attained nibanna, but here we are, subject to samsara.
we can conclude from our experience that samsara is "real" (insofar as the cycle of birth and death is actual -- or if one understands samsara to be simply this circumstance of being subject to suffering).
In the traditional sense of "exists", samsara either "exists" or "not exists" -- it doesn't make sense to change according to circumstances (eg. when an event happens, like attaining nibanna).
The "cessation of samsara", insofar as we are talking about the Buddha attaining nibanna, is not the cessation of our reality, nor the cessation of the samsara we are subjected to.

Does this mean, that when you attain Nibanna, samsara does not exist, and neither it exists for the other beings in samsara, because Nibanna is unconditioned, so there is no samsara, and consequently there are no beings?

Beings "don't exist" in the traditional sense; beings are anatta. But we are certainly alive -- we are not imagination.

user295: Samsara exists based on mind-matter phenomena. Any phenomena which is part of mind, mind content, matter comes under ultimate truths (truths that not fall apart under divisibility into its constituent components or indivisible). So it is an ultimate truth that samsara does exit when you are part of it if you are worldling.
When you attain Nirvana which is unconditioned, then you are out of samsara. For some one who attains Nirvana this also is an ultimate truth.

user5191: Samsara is just a word. There is seeing, hearing, tasting, feeling, smelling, and thinking. And there is the UN enlightened mind that misapprehends the true nature of these phenomenon. 
edit for your edit : 

does not exist but it exists for other beings in samsara?

There are four things without bounds; the knowledge of a buddha, space, the universe, and the world of beings.  Therefore, samsara will never be extinguished. In this way, enlightenment is like a forest fire, burning down an endless forest.
I COULD tell you the timestamp for my reference; but instead I'll make you watch through the entire thing, enjoy!

user43: The traditional Mahayana formula is that "Samsara is Nirvana". This is explained in depth in Madhyamaka literature. Here is one quote from Jay Garfield commentary on his translation of Nagarjuna's Mulamadhyamakakarika:

It is [possible] to grasp after nirvana – to reify it as a state and to crave it as a phenomenon inherently different from samsara and as highly desirable since it is indeed characterized as liberation from suffering. But this grasping onto the end of grasping is itself a grasping and so precludes the attainment of nirvana. Nirvana requires, according to Nagarjuna, a complete cessation of grasping, including that onto nirvana itself. While that might seem paradoxical, it is not: To grasp onto something in this sense requires, inter alia, that one reify it. By refusing to reify liberation, in virtue of seeing it as the correlative of bondage, which itself is not inherently existent, it is possible to pursue the path to liberation without creating at the same time a huge obstacle on that path – the root delusion with regard to nirvana itself.

And from Master Dogen's Genjokoan:

When everything is buddha-dharma, there are Samsara and Nirvana, Path, birth and death, Buddhas and sentient beings. When myriad things are without self, there is no Samsara, no Nirvana, no Buddha, no sentient beings, no birth and no death.


5000: <p>Does samsara exist? Or does samsara not exists and it just looks to us that it exists, but in reality it is all the same "thing"?</p>

<p>Here's the updated question, to make it clearer:</p>

<p><strong>UPDATE</strong></p>

<p>Nibanna is the cessation of all that is conditioned, i.e. samsara.</p>

<p>As I understand it, when you attain Nibanna which is unconditioned, then you are out of samsara.</p>

<p>Does this mean, that when you attain Nibanna, samsara:</p>

<ol>
<li><p>does not exist but it exists for other beings in samsara?</p></li>
<li><p>does not exist, and neither it exists for the other beings in samsara, because Nibanna is unconditioned, so there is no samsara, and consequently there are no beings?</p></li>
</ol>

<p>Which one is it? 1 or 2?</p>
 5513: <p>When we wake up from dream, does it exist for others?</p>
 -1: <ol>
<li>Samsara exists. 2. Samsara does not exist. 3. Samsara both exists and does not exist. 4. Samsara neither exists nor not exists. All of these statements are true. All of these statements are false. All of these statements are both true and false. All of these statements are neither true nor false.</li>
</ol>
 7090: <p>Samsara exist because there is enlightenment- free from Samara.</p>

<p>Just like wealth exist because there are poor. </p>

<p>Only if one is free from Samsara can one see Samsara. </p>

<p>If everyone is in Samsara, then how can one see Samsara? </p>

<p>That is what Buddha is here to teach </p>
 7525: <p>Excerpt from &quot;<em>Lamp of Mahamudra</em>&quot; by Tsele Natsok Rangdrol:</p>
<blockquote>
<p>&quot;Section One - Ground Mahamudra&quot;</p>
<p>&quot;The View&quot;</p>
<p>&quot;Your natural essence cannot be established as either samsara or nirvana.  Not confined by any one extreme, free from the limitations of exaggeration or denigration, it is not tainted nor spoiled by such designations as pleasant or unpleasant, being or not being, existent or non-existent, permanent or annihilated, self or other, and so forth...</p>
<p>Yet, no matter how it manifests, ultimately this essence has no true existence...</p>
<p>It is the actual basis of all that appears and exists, the whole of samsara and nirvana.</p>
<p>When you realize its nature, knowing its real condition, you are called a Buddha.  When you do not realize it, remaining ignorant of it and experiencing confusion, you are called a sentient being.&quot;</p>
</blockquote>
<p>For any who are interested, &quot;<em>Lamp of Mahamudra</em>&quot; and &quot;<em>The Heart of the Matter</em>&quot;, both by Tsele Natsok Rangdrol, have been combined in a single book, entitled &quot;<em>Heart Lamp</em>&quot;, translated by Erik Pema Kunsang, Rangjung Yeshe Publications, North Atlantic Books.</p>
 471: <p>From <a href="https://suttacentral.net/sn15.3/en/sujato" rel="nofollow noreferrer">SN 15.3</a>:</p>
<blockquote>
<p>“Mendicants, transmigration (<em>samsara</em>) has no known beginning. No first point is
found of sentient beings roaming and transmigrating, hindered by
ignorance and fettered by craving. What do you think? Which is more:
the flow of tears you’ve shed while roaming and transmigrating for
such a very long time—weeping and wailing from being united with the
unloved and separated from the loved—or the water in the four oceans?”</p>
<p>“As we understand the Buddha’s teaching, the flow of tears we’ve shed
while roaming and transmigrating is more than the water in the four
oceans.”</p>
<p>“Good, good, mendicants!</p>
</blockquote>
<p><em>Samsara</em> exists and it has no beginning.</p>
<p>Who shed the tears for such a long time, that could exceed the four oceans?</p>
<p>It's the self. The mental idea of the self. It's the self that experiences <em>samsara</em>.</p>
<p>For whom does <em>samsara</em> exist? It exists for the self.</p>
<p>If there's no self at all, there's no <em>samsara</em>.</p>
<p>If there's self, there's <em>samsara</em>.</p>
<p>So, basically, <em>samsara</em> exists dependent on mind-body phenomena. So long as mind-body phenomena exists, so does <em>samsara</em>.</p>
<hr />
<p>Also at the same time, <em>samsara</em> doesn't <strong>really</strong> exist. Why?</p>
<p><em>Sabbe dhamma anatta</em> - all phenomena is not self.</p>
 -1: <p>If you use "exists" in the Buddhist context, you might be understood as "has own, unconditioned essence" which is the traditional use -- here, the object in question cannot suddenly become or unbecome according to circumstances, because it always "is". Or as "is real / refers to an actual experience" which is the more popular understanding. Not being explicit about how this word is being can be confusing.</p>

<p>Having said that, to the questions:</p>

<blockquote>
  <p>Does samsara exist? Or does samsara not exists and it just looks to us that it exists, but in reality it is all the same "thing"?</p>
</blockquote>

<p>I'm understanding samsara here as a word to describe the cycle of birth and death. </p>

<p>Whether it "exists" -- in the traditional sense -- or "not exists" is a philosophical topic whose answer might change according to the philosophy of each school (though I think no school who would declare existence of phenomena or concepts have survived).</p>

<blockquote>
  <p>Does this mean, that when you attain Nibanna, samsara does not exist but it exists for other beings in samsara?</p>
</blockquote>

<p>from the following:</p>

<p><code>The Buddha attained nibanna, but here we are, subject to samsara.</code></p>

<p>we can conclude from our experience that samsara is "real" (insofar as the cycle of birth and death is actual -- or if one understands samsara to be simply this circumstance of being subject to suffering).</p>

<p>In the traditional sense of "exists", samsara either "exists" or "not exists" -- it doesn't make sense to change according to circumstances (eg. when an event happens, like attaining nibanna).</p>

<p>The "cessation of samsara", insofar as we are talking about the Buddha attaining nibanna, is not the cessation of our reality, nor the cessation of the samsara we are subjected to.</p>

<blockquote>
  <p>Does this mean, that when you attain Nibanna, samsara does not exist, and neither it exists for the other beings in samsara, because Nibanna is unconditioned, so there is no samsara, and consequently there are no beings?</p>
</blockquote>

<p>Beings "don't exist" in the traditional sense; beings are <em>anatta</em>. But we are certainly alive -- we are not imagination.</p>
 295: <p>Samsara exists based on mind-matter phenomena. Any phenomena which is part of mind, mind content, matter comes under ultimate truths (truths that not fall apart under divisibility into its constituent components or indivisible). So it is an ultimate truth that samsara does exit when you are part of it if you are worldling.</p>

<p>When you attain Nirvana which is unconditioned, then you are out of samsara. For some one who attains Nirvana this also is an ultimate truth.</p>
 5191: <p>Samsara is just a word. There is seeing, hearing, tasting, feeling, smelling, and thinking. And there is the UN enlightened mind that misapprehends the true nature of these phenomenon. </p>

<p>edit for your edit : </p>

<blockquote>
  <p>does not exist but it exists for other beings in samsara?</p>
</blockquote>

<p><a href="https://www.youtube.com/watch?v=O6Isd8tSOXw" rel="nofollow">There are four things without bounds; the knowledge of a buddha, space, the universe, and the world of beings.</a>  Therefore, samsara will never be extinguished. In this way, enlightenment is like a forest fire, burning down an endless forest.</p>

<p>I COULD tell you the timestamp for my reference; but instead I'll make you watch through the entire thing, enjoy!</p>
 43: <p>The traditional Mahayana formula is that "Samsara is Nirvana". This is explained in depth in Madhyamaka literature. Here is one quote from Jay Garfield commentary on <a href="http://rads.stackoverflow.com/amzn/click/0195093364">his translation of Nagarjuna's Mulamadhyamakakarika</a>:</p>

<blockquote>
  <p>It is [possible] to grasp after nirvana – to reify it as a state and to crave it as a phenomenon inherently different from samsara and as highly desirable since it is indeed characterized as liberation from suffering. But this grasping onto the end of grasping is itself a grasping and so precludes the attainment of nirvana. Nirvana requires, according to Nagarjuna, a complete cessation of grasping, including that onto nirvana itself. While that might seem paradoxical, it is not: To grasp onto something in this sense requires, inter alia, that one reify it. By refusing to reify liberation, in virtue of seeing it as the correlative of bondage, which itself is not inherently existent, it is possible to pursue the path to liberation without creating at the same time a huge obstacle on that path – the root delusion with regard to nirvana itself.</p>
</blockquote>

<p>And from Master Dogen's Genjokoan:</p>

<blockquote>
  <p>When everything is buddha-dharma, there are Samsara and Nirvana, Path, birth and death, Buddhas and sentient beings. When myriad things are without self, there is no Samsara, no Nirvana, no Buddha, no sentient beings, no birth and no death.</p>
</blockquote>
