This may be a dumb issue, but I have no other way to find out. At some point I was sent a facebook message from someone with a name of a person I knew, who wrote something along the lines "haha I found this old photo" and a link.
A year or two later, I found the Google series on how they were hacked, and in their first episode (EP000)
they described exactly the same thing. Someone clicked a link that looked similar to what I got, around (5:14) in the video. Eventually they figured out that the Chinese Gov was involved (15:15). The motivation being as simple as spying on people that advocate for human rights in China.
Anyways, sometimes I notice my PC being slowed down significantly, and today again. Things start to lag, especially whenever I use the browser, no matter which browser. But my task manager shows no suspiciously large activity on the ethernet tab, or any tab. My cache is cleared, my PC restarted, doesn't change a thing. At some point it will recede again. It happened a couple times now.
I don't know how to track devices that are using my network. The router webpage tells me which devices were connected at some point, but I can't see or figure out how to see who's been using my network over time to figure out whether today there was a device in use that I do not know. Or which servers I was connected to during the week. Maybe I'd find an outlier.
Sorry for this rather long text, but I am somewhat paranoid because I do not know how to find any information on how to help myself with this issue.
Edit: So, reinstalling Windows is a solution, but if there is any means to find whether I was attacked, for the sake of learning, I'd love to know.