user20640: Sometimes i am keeping some mental object in mind, free from anger or greed, and for a moment i feel piti and sukha over my entire body. Sometimes this piti and sukha keep with me for a long time.
But even in first jhana i keep my mental object in mind, like blue kasina (whondering world all blue) or parts of body.
Sometimes the piti and sukha leaves.
I read that after the first jhana we need to abandon the vitakka and vicara. But how?
I need to keep my focus in some mental object or just let the things go at their own pace, in my mind.
How to i reinforce the upper jhanas if i need to abandon the mental objects?
Ps: sometimes i feel piti and sukha, when concentrate into the kammathana, both in public and in my cave (bedroom).

user16297: 
I read that after the first jhana we need to abandon the vitakka and vicara. But how?

The practice you're doing, is based on Vism. and their redefinition of jhāna, vitakka, etc.
If you want to follow the Buddha's definition of jhāna, then you have to follow the buddha's definition of vitakka so you know what V&V is in first jhāna and what you are removing to enter second jhāna, as described here: (my collection of notes, contains links to all the sutta passages that use vitakka in jhāna context)
https://lucid24.org/sted/8aam/8samadhi/vitakka/index.html
If you prefer to follow the LBT (late buddhist teaching) redefinition of 'jhāna', then just keep doing what you're doing, and it will improve naturally. They redefine 'vitakka' and vicāra as the subverbal attention on your kasina. As you become skilled in staying on the kasina with very little effort or resistance, that's the gradual  removal of V&V. Vicāra is redefined as keeping your attention focused on the kasina. "second jhāna" with V&V removed is redefined to mean you no longer had to exert so much force and energy to keep your mind from drifting away from the kasina.

20640: <p>Sometimes i am keeping some mental object in mind, free from anger or greed, and for a moment i feel piti and sukha over my entire body. Sometimes this piti and sukha keep with me for a long time.</p>
<p>But even in first jhana i keep my mental object in mind, like blue kasina (whondering world all blue) or parts of body.</p>
<p>Sometimes the piti and sukha leaves.</p>
<p>I read that after the first jhana we need to abandon the vitakka and vicara. But how?</p>
<p>I need to keep my focus in some mental object or just let the things go at their own pace, in my mind.</p>
<p>How to i reinforce the upper jhanas if i need to abandon the mental objects?</p>
<p>Ps: sometimes i feel piti and sukha, when concentrate into the kammathana, both in public and in my cave (bedroom).</p>
 16297: <blockquote>
<p>I read that after the first jhana we need to abandon the vitakka and vicara. But how?</p>
</blockquote>
<p>The practice you're doing, is based on Vism. and their redefinition of jhāna, vitakka, etc.
If you want to follow the Buddha's definition of jhāna, then you have to follow the buddha's definition of vitakka so you know what V&amp;V is in first jhāna and what you are removing to enter second jhāna, as described here: (my collection of notes, contains links to all the sutta passages that use vitakka in jhāna context)
<a href="https://lucid24.org/sted/8aam/8samadhi/vitakka/index.html" rel="nofollow noreferrer">https://lucid24.org/sted/8aam/8samadhi/vitakka/index.html</a></p>
<p>If you prefer to follow the LBT (late buddhist teaching) redefinition of 'jhāna', then just keep doing what you're doing, and it will improve naturally. They redefine 'vitakka' and vicāra as the subverbal attention on your kasina. As you become skilled in staying on the kasina with very little effort or resistance, that's the gradual  removal of V&amp;V. Vicāra is redefined as keeping your attention focused on the kasina. &quot;second jhāna&quot; with V&amp;V removed is redefined to mean you no longer had to exert so much force and energy to keep your mind from drifting away from the kasina.</p>
