Stuck : my webpage doesn't scrool down ! I already looked everywhere

I am making a webpage but i'am not a expert one. Everything is going fine but i've myself with a problem that i can't fix.

My webpage scrool up but it doesn't scroll down. I've been looking around in the forum, reading most of the answers and applying the solutions but, so far, i still doesn't scrool down. It must be a new problem here. Can anyone help me out here please ?

I am adding my html and css files bellow. thanks in advance

HMTL5

style.css