Have white space between my background image and footer

I have tried everything, but can’t find a solution.
On my contact page, I am using contact form template and when I upload background image I have white space between my image and footer, have tried different settings.I did make sure the image is big size and made sure to put full screen settings, but nothing seems to work
And have the same problem on my home page when minimize the window, that wite line appears again. I have a high resolution screen, but shouldn’t be a problem
And it looks fine on a cellphone