Hi, welcome
Actually your English is pretty good.
Us humans can be surrounded in a room full of people and still be lonely. As intelligent animals we criticise ourselves and try to live up to expectations and that puts pressure upon ourselves a lot. Hence why you feel the way you do.
School can have a domino effect, where one problem leans on another and another. Like, losing interest at school for any reason and that results in low grades and that leads to parents concerns which leads to low self esteem for you. The remedy can be simple or complex. Eg it could be simply focussing on homework and school lessons and all might work out or- it could be changes in a teenagers life which are complex and difficult to deal with like body changes and things like pressure from friends etc that need more unravelling to get to the bottom of things. The latter can need professional help like a counsellor. Have you got a school counsellor you can talk to? If so then I'd jump at that opportunity.
Sometimes things in life go through a cycle. Your passion from school hasnt disappeared, it's just taking a holiday. So it will return and you'll benefit from knowing what its like to lose interest in things, that you will recover and you will like it again.
I hope I've helped.
TonyWK
