Blog post are overlapping with widgets

Please I'm being driven crazy here, my posts page is not displaying correctly, the widgets (on the side bar) are overlapping with the blog posts and no matter what I do to increase the global theme background, it doesn't seem to change. For example, the posts background is consistently remains at 1080, no matter what I do. Please help, the codes are driving me mad.

Also on mobile phone, the website is displaying with an infinity of free spaces to the right.

I really appreciate you help, thanks

Thank you!