Im new to Unreal Engine and i dont know what to do.
Every time i go in Playmode or Rebuild the lighting the textures get scrambled.
That is very strange, it seems like the UV maps are messed up. The walls, are they actual meshes (fbx files), or are they something else?
everything is in fbx. Its good in the editor but if I go in playmode that happens, and its always scrambles the textures randomly.
How are textures and materials assigned. Are they placed on each mesh in the details panel, or do you have some algorithm for it?
Are you only building lighting?
i only build the ligting but the method of placing the material does not matter. its always bad.
if only one fbx is present it works fine, but as soon as i place an other fbx starts the scrambling.
What hardware are you using, CPU, GPU, amount of RAM, etc? 
i5 10400f, RX 5700XT, 16GB 3200Mhz, 1TB Samsung m2, 2TB WD Blue
Hmm, you should have enough VRAM to do all this. I know it’s a pain, but if you export the scene and assets to a blank project and do the light rebuild. Does the same issue happen?