Quote Originally Posted by it-ogo View Post
я хочу приехать - I want to come (right now).
Right now? Why not "in a year"? Я хочу приехать сюда через год.
ты не можешь слушать – you are unable to listen (you are deaf)
If he is deaf he can listen, he cannot hear. He cannot listen because he's talking on the phone rather.

That's what I've just said: it's a problem to explain perfectiveness without seeing the context and just making it up from a couple of words given to you.

ты не можешь послушать - you can't listen (what I am talking to you because you go away right now)
No. The speaker's meaning is: you can't spend a certain amount of time to start listening to me and finish listening. Even if he is leaving he can listen, but can't be listening to some logical end.

я стараюсь понимать – (Usually) I try to understand (their way of thinking)
Noooo. Я стараюсь понимать can mean both I try to understand and I'm trying to understand.
Besides, that means I'm being in the process of focusing my attention in attempts to grasp the idea. I'm trying not to distact while i'm listening or reading. That's it.

я стараюсь понять - I am trying to understand (what you told me last time)
The same as above. Besides that means I'm trying to understand something and have an idea of that as a result of listening or reading.

я должен работать - I must be working (otherwise they will call me lazy bones).
You could say Я должен поработать meaning the same reason.

The reason of using perfective or imperfective verb forms is absolutely different.