HELP!?!?!?!? quick answer please (details inside)?

Take a deep breath. Ok now remember high school it hard. There are heaps of different kids and it was only your first day. Tomorrow look for more mature kids your age ( there are sure to be some ). As for it being hot and crowded that's just school you will get used to it. If thing's don't get better and you think it's just a bad school and not right for you ( wait a few weeks and see first) then try talking to your mum about what she thinks maybe you should try a different school that mite be better suited to you. Good luck.