The normals are fine.

I tried to import in different methods now, and I found out that it is working by importing in OBJ with all the options unchecked. Like material and everything.

So I...

Ouh yes you are right. The long box is totally fine.
Just the 2 imported objects.
I already checked everything through the Attribute Spread Sheet. Everything is exactly the same.

What can be...

So i modeled 2 new boxes. 1 smooth the other normal bevel.
Everything seems fine.
The VW Beetle and the "wireframe"cube were imported from another scene. But the long box left to the wirecube was...

Also checked that. Nothing that could cause the problem

Very good Point, but unfortunately I only have the masterlayer set up.
Now i tried to make a new layer with all objects but the same problem.

The objects have the same material but except for...

Hey Guys! :)

I have set up a user ibl env, backplate etc...

Now i have the checkerboard as a ground and another plane for the shadows.

I installed some additional arealights to increase...