Hamburger Menu pinned to site creates a black bar when opened in the lower sections of the site (images included)

As you can see in this imagee, there is a black bar when I open my Hamburger Menu. This doesnt happen in the first section, which is its position in the editor. I can only see this in preview or live, not in the editor. The Menu is pinned to the site. Does anyone know what the problem could be? The black bar pushes down the background images (which have a parallax effect), in closed state the image would be at the top.