For about 1 month, my laptop has always reset after every restart
All settings gone, logged out everywhere, all files away from all programs
Sounds like your profile can't be loaded, damaged. Then Win loads a temporary profile, with which you can't save anything.
I don't get this error message. I have already lost some files that were very important.
Whenever something unusual happens, I think of "potentially unwanted programs", the so-called "PuP's". No virus in the real sense, but only has the task of annoying, common in the matter, it can open the door to the PC for the viruses.
Download the ADWCLEANER, ideally from "Heise.de" and let it run through, then the CCleaner so that residues are removed - use the cleaner with care and check what it deletes.