(HTML or CSS) White background color is going lower than my last part of code

Hum, hey ! I got something that I tried to fix for almost four hours, but I couldn't find it. The worst thing is that i'm almost sure that it is a stupid thing to remove or to replace, but I don't know. So Is there is a way to make my background stopping on the last image or if it's a problem in my code, is there is a way to fix it? I'm placing the code. Thanks in advance ! (my code may be horrible, sorry if that's the case ^^)Hum, hey ! I got something that I tried to fix