SOLVED!
Hi,
Problem solved.
I don't know what it was in final.
I did these Steps:
1. I Installed the Direct X Runtime Version i downloaded at Microsoft
2. I Reinstalled Pitool (Software and Drivers for Pimax Headset
3. I Deinstalled Steam VR, Cleared Folders, cleared Registry, Reboot and did a fresh Install of Steam VR.
I'ts looking good! Maybe this can help others too.
Always a clear Sky,
Tomkin