Help on Uv mapping and light

Hello all,

Sorry if you found my question boring but I’m a biginner.

I have an issue when I try to add my mesh near the same other mesh (a wall). Some black shadow appear I think it’s a problem of UV or light map but I don’t find the solution. I tried several time solution like below

1 - use the same mesh with Uv on entire surface
2 - create 3 wall in blender end do unwrap with the 3 same face selected.
3 - same as 2 but with margin of 0,001
4 - make island
5 - use mark seams but maybe I don’t yet understand verry well how this works.

Sorry I’m French haha

I watched a lot of video on YouTube but not yet found the solution of my problem, so it’s why I try on this forum.

I done the biginner tutorial of unreal.

No problem with other basic color material only when I use an brick material or concrete…

I try also to change shadow parameter but not the solution.