Hello Francisco, hello Albert, this might be the same as in bug #996726 and not directly related to the nvidia driver.
I hit a crash in kwin_x11 with an AMD graphics card and could workaround by installing libkdecorations2-5v5_5.21.5-2_amd64.deb like mentioned in #996726. Kind regards, Bernhard https://bugs.debian.org/996726
