I opened the first thread yesterday, but it got closed (abandoned?). I wanted to reply to your people’s comments and give an update.
First, thanks for all the good tipps, I think you are right and only a fresh install will make sure nothing is left. It’s been two days where I let this PC running again and nothing happened so far. Except, Microsoft Edge is back on it, thank you Windows… But I can’t be entirety sure.
Second, u/I_need_happiness posted a really good reply and I think he was right that it wasn’t a human controlling my pc, but kind of a script that took over. At least it makes sense, because why would someone make such an effort to fail so miserably. Also there’s literally nothing to get from me or my PC, so not worth any effort.
Third, I remember having downloaded a fake open office update several months ago. I noticed something was wrong back then and deleted it, but somehow it persisted. Nothing happened since then, so I didn’t think about it anymore. There’s a German website faking the original website. Adwcleaner found the “PUP.Optional.Fake.OpenOfficeUpdater” somewhere once again.
Maybe it was this or maybe it opened the door for more, although I couldn’t find anything else. Gonna do some backups and then reinstall Windows, but I do feel safer again knowing that not that much has changed and you cannot just get invisible viruses and trojans our of nowhere.
Cheers