Can't add psd files to my projects anymore

Then you must have had a really corrupt profile somewhere -

ya i was actually suprised that it made a diffrence, but hope that this fixed it. 

Glad you got it running, but the working color space is actually not important. The embedded profile will always override that.

As long as a document has an embedded profile, that profile will take precedence over the working space. If you're pasting, it gets automatically converted to the base document profile.

The Place command creates a smart object, where an embedded smart object retains its original profile, even if the master file has a different profile.

The point is - I don't know what the problem was here, but color spaces wasn't it. It's something else.  

yeah that was just to try to see if it made any difference

I actually fount the solution. 

the fresh installed PS uses a differen working colour setting then my saved .psd. So they differed after i opend one udn thend PS that i want to change to the working one, but my other file that i wanted to add, still had a different embedded one. I hope that makes sense, english ist not my first language :-), 

allowed Photoshop to use up to 100% RAM

By @angelas59768293

Never do that. It will choke the whole system. Dial it down to max. 70%.

You always need to leave sufficient memory for other processes and applications.

You also need to describe exactly what you're doing.

Can you open these PSDs? (File > Open, or double-click)

Are you using the "Place" command to add content to an already existing open document?

Somehow the embeded color was the issue, no idea why they where different all of a sudden 

Sadly, this didn't fix the issue

remove and reinstall the creative cloud for desktop app.  



https://helpx.adobe.com/download-install/apps/download-install-apps/creative-cloud-apps/download-creative-cloud-desktop-app-from-web.html