I'm glad you got the feedback and support you needed. German Harry Potter fandom sounds like an awesome place, and I applaud it from afar, since my German is straight up awful.

The thing about Mary Sues for me is - it takes a really deft hand to make me like someone else's. Like, I've had my own over the years, and I liked them, but they tend to work for an audience of one. I'm not saying it can't be done well (and self-insert can also be done so well you barely notice it), I'm just saying that is one HELL of a mountain to climb. (To make it work for me. Other people may love Mary Sues without restriction! But for me, they're always going to be a tough sell. Doesn't mean people shouldn't write them. Hey, we all have, right?)