I downloaded the Peruvian Lighthouse theme and installed it. Then I tried to install another theme, but the configuration screen was dead, did not respond anymore, could not be closed either.
So I logged out and logged on again and the Peruvian theme was active. But what a mistake! The inactive screens are almost invisible, so I decided to go back to the Breeze theme. And that does not work.
Even if I select the Breeze theme and click on apply, logout and logon, the peruvian theme is still active
When I select the dark breeze theme, the menus are dark, ok, but inactive screens are still nearly visible.
How can I reset to the breeze theme?
Where is the theme stored? Perhaps I can remove it or overwrite it with something more useable.

I use Gentoo linux, plasma 5.3.1 and the most recent of everything.

edit: I was wrong. I installed the Aya theme and tried the peruvian them later but that did not change anything.
So if anybody knows how to restore the standard theme, or how to remove the later installed themes.. please tell me.

Well.. it is solved somehow by changing a desktop effect: tranparency
Ok now I can try some more themes