Perhaps (adv): used to express uncertainty or possibility. Maybe, it's possible, it could be.
Meanwhile (adv): in the intervening period of time, at the same time. For the moment, for the present, int he meantime.
Nevertheless (adv): in spite of that, all the same time. Even so, however, despite that, though.
* I don't know if it is my problem or like a friend said, it is the evolutions of the knowledge or the differents steps that the brain has when it is learning something. The thing is that i have been feeling stander, I mean, I feel like my brain doesn't want to recieve more information, it is saturated. Sometimes it is so serious that I thought: ''I don't understand anything''. I hope this sensations will disappear as soon as possible.