[Deque]

Welcome to this forum. Your introduction is what I call a great introduction. If just every introduction would have a slice of the quality of yours, this section would be much more interesting.
You get a big fat fresh coffee by me.

I hardly stand negative or „constructive” criticism but if it's true I accept it particularly as I'm always perfectionist and if I do something, I want to do it well and be excellent in it.

Standing criticism (constructive or not) is something you can learn and exercise very well in forums. I am a sensitive person and haven't always been that distant to criticism, especially when I was a teenager, but after years of dealing with criticism (in literature and arts) I also moved to seeing them as very useful and an opportunity to improve my skills.

Forums have the advantage that you can take your time until you answer. So if you feel offended, don't answer immediately. Let some hours pass, maybe days and get some emotional distance to the post. Or just wait for your mood to turn into a good one again. Is the post constructive? Then reframe your view about the person posting it from an offense to an effort in helping yourself to improve. I think the hardest part about all that is to be able to wait with your response.

Is it not constructive? In that case the person might not even worth to answer to. Stand over it, even if you have a hard time to do so emotionally. Some people really want to offend and will see a victory if you let them know you are hurt. Don't let them feel like they won, demonstrate that you are not hurt. Others are trolls, these need to be ignored constantly as tempting as it is to react. Others may just have been hurt as well because of a misunderstanding and overreact. They will calm down and sometimes appologize if you react friendly despite their post.
This is the best playing field to work on your own capabilities in dealing with criticism. It will reflect in the world outside the internet as well.

That said, welcome to HC.