I've had this issue for a while now, since I thought I could fix it myself. Almost all my programs have lost their icon image, which is not fixable by applying a different icon theme unfortunately. Just installed the Reversal icon pack to test that. My settings are attached here, sorry for the german:
I am assuming this is due to some of the weird behaviour I have had for some days months ago. Gnome would just not load and instead show me an error screen. So I had to uninstall gnome entirely, then reinstall it and that magically fixed it, but my icons were gone.
Aside: You don't ever need to apologise for your native language 😊
even germans?
Especially Germans, and your cousins who live in the swamp next door.
We can't help the fact our languages just arent't that elegant, no need to apologize for it.