>What is pleasure?
The state you are temporarily in when you meet a want or need.
However this also amounts to boredom as your need has been met and you no longer have the driving force of want/need.
In other words, you are constantly deprived and in pain, pleasure temporally makes you stop suffering; however this is felt by a person as a state of normalcy.
Pleasure is the void left when you eliminate pain. And it feels just like that, a void.
>Why and how do we feel it(I'm also looking for biological answers here if you guys can provide)?
I think you mean neurological, as in dope; though i'm not experienced enough to elaborate.
But philosophically we feel it due to the meeting of our inborn natural impulses (however perverted from nature they may be)
>And when we feel it, why do we want it to last forever?
Because otherwise we are in agonizing pain.
>Should we chase it and try to live our lives with always pleasure, or try to keep away from it as much as possible?
This I do not know.
Up to you really.
>How does hedonism affect a man?
I makes him bored.