OBJ Import on Unity 2018.2.15

Dear Unity users,

first things first: I’m never sure where to best to post my question/problem.
Thus I repeat the problem here. When importing a simple obj file (hexaeder)
some sides of the hexaeder are distorted, see here:

https://forum.unity.com/threads/obj-import-on-unity-2018-2-15.582613/

Any suggestions?

Best wishes,
SG

Seems to be that I used the wrong Shader.

Resolved.