desperate , need some help !

hello everyone , i joined the forum because i'm desperatly in need of some help!
I'm new to css/html and i managed to make a website ( nicklauwerijs.zxq.net)
but i have a problem , when you open the website you can scroll to the right and you can see that the background
isn't the same width as the header and you have a white space next to it !
how can i get rid of this? i've searched sick to solve this problem but nothing worked !
please help me ! ill be thankfull forever !