Ok maybe it helps some others too. Got mine running again.
I turned off my Power supply unplugged everything let it sit for a couple hours hooked everything together again. And suddenly it started working again. I was already at the point of taking the gpu apart but gave it a last try.
The strange thing is on this bootup it did the same thing as bevor when nothing worked. Only one white line on the screen red led error code on the mainboard for gpu and complete loss of video signal but afer 10-15 sec. The msi logo showed up and it took unusualy long to boot but it did eventually boot. Hopefully it will stay running now!