UMG Buttons not having Focus

I have the problem that I use RightClick for my Camera Rotation, and also have UMG Buttons on the Main viewport. The Problem now is, that if I want to use the Buttons, I have to double-click them, one click to get them in Focus and a second one to actually click them. I already set “Input mode Game and UI” in BeginPlay
Hopefully someone knows a fix for that, thanks.