How can a would-be researcher overcome slow comprehension, obsession and poor communication skills? I m a current master coursework student in engineering major and I’m planning to do a PhD after graduating from this course. I want to know how to become a qualified researcher. There are several shortcomings that I think may stop me making it:


I understand things very slowly. When I read or listen to others, I can’t get the idea very quickly. Sometimes there is even an unexpected blank or distraction in my mind when I’m getting some information and I have to get it again.
I like delving in solving a certain question I’m interested in, but I often get stuck there for a long time until I solve it, which really have a severe negative effect on exams. In addition, this kind of obsession is a short-term effect, rather than perminant one. That’s to say it’s hard for me to stick to one thing for a long period of time as I’m easy to get obsessed in another thing once it appeals to me.
I’m not good at explaining or illustrating my idea to others. They often don’t understand what's my point and I need to explain it several times. The situation is worse in speaking. I often get a blank mind and forget the next point to connect to my current point when I express my idea orally. It’s very hard to organize my idea well when speaking.


Since I have no experience of being a researcher, I want to know if those problems are likely to be a barrier to becoming a qualified researcher? How can I overcome these problems?
As @ff524 mentioned in comments, it's hard to give advice to you after only these few lines, for no reason more than that what you describe as holding you back might equally well be a sign that you share certain characteristics very common among academic researchers. 

As to 2), you essentially say that you like digging into a problem until you have a solution that pleases you, while forgetting the world (exam) around you. That ability, or obsession, must be one of the most important for a researcher, whatever the source (it could point to some excessive OCDness). It currently probably leads to you having crack answer to a few exam questions, while none or marginal ones to others, and so might prevent you from ever being a researcher. All it seems to take though is to keep reminding yourself to not obsess: write an answer outline to all questions, and then allow yourself to drill deeper. It's essentially an inability to multi-task, and there is lots of advice online how to address that. 

The difficulty to orally communicate you mention in 3) is extremely common among professors. Your ability to speak can be improved in rhetoric classes, but being a poor speaker is often linked to issues such as anxiety too, and so is tricky. Communicating clearly in writing though can be easily improved in self-study. Get yourself a copy of Strunck&amp;White, skip the 4th chapter, and ignore those telling you it's outdated. Zinsser's On Writing Well is even more helpful. It was a real life-changer for me. 

Your issue 1) is unclear for someone not knowing you in person as well. You understand slowly. Says who? By comparison to who? Does the person explaining things to you suffer from your issue 3) as well? You might just be too hard on yourself. I had few teachers who truly helped me understand what I had to learn better, so few that all these years later they and what they said stick out in my memory. In terms of comprehending from reading, you seem to say that to truly learn, you need to re-read your books. That isn't too uncommon either. Additionally, from what you say in 2) which might allude to some OCDness or similar, you might be too harsh on yourself in judging when you have "learned" something. To this day, when I read a math book I have to fight feeling that I didn't read it carefully enough if there is any proof in it I couldn't provide on the spot. That's counter-productive. 

I hope some of what i wrote actually fits your situation, or at least helps you maybe view it in a different light.