Artifacts and weird shadows

Hello everybody, I have these strange shadows on my model. When I turn off Direct Light, the artifacts disappear. I’ve looked around, but nothing has really helped. Is it because of the normals?
On some walls, I have a shadow even though there is no object there.

I hope you can help me.

Best regards

That’s usually because of overlapping geometry or low shadow bias on your directional light. Try to nudge the shadow bias of the light up slightly or soften the source angle. If that doesn’t do it, check your mesh for double faces or bad normals—cleaning those up usually fixes the weird shadows right away.