Many White Screens from Plugins to Updates

Hello,
I don’t know where to start: the problem are White Screens. I’m not able to work with my site properly. The Dashboard or Pages page don’t load properly and in most cases, there is just a White Screen popping up. Especially every time I click on “Plugins” or “Updates” … its frustrating. Please help me.

I can’t specify the problem any further, because I encounter it on so many different levels.

Is there anything I can do to analyze the root of the problem and get rid of it?

Thanks in advance!