One simple Quest project?

Thank you, and I already did. But I am running into multiple issues.

It’s a super simple setup, just with primitive objects.

Below, you can see problem Nr.1: Black Artifacts on intersecting edges.

VIDEO EXPLANATION:
[Oculus Quest - Test Development Android ES3.1 / Vulkan - YouTube

Oculus Quest - Test Development Android ES3.1 / Vulkan - YouTube](Oculus Quest - Test Development Android ES3.1 / Vulkan - YouTube)

Updated Scene File:
In my latest Project File, I added a rotating head-sculpture. I wanted to see the performance when an object is rotating. However, the “black artifacts” don’t have anything to do with it and still remain even by having just a few primitive objects in my scene file.

DOWNLOAD PROJECT FILE:
https://mega.nz/#!gWJREKYI!XIlBMFzjC…FQJBhPN-RzzBE8

My full documentation can be found here:

Any ideas how to resolve the issue with the “black edges”?
Thanks for any little hint and help and happy pixeling!