Problems with walls overlapping causing.....(see img)

Hi sorry i could be more specific cause I’m still quite new to unreal

but heres the problem (see img). How do I fix it?

it’s called stitching or Z-Buffer flickering.
The Problem is, that your faces occupy the same space, so the computer simplyfied can’t decide what face to draw in that area.

Best way to avoid this is editing your Mesh, and get rid of those overlapping faces. If you use multiple meshes, make sure they fit, and avoid overlapping.