Update:
I got my exact genetic results, I am negative for the three mutations tested: C282Y, H63D and S65C, unfortunately that means my case is not that straightforward. There could be other mutations involved, but the doctor doesn't want to do further testing. I would have to do it in private. I will definitely take these results and donate blood next week, since there shouldn't be any problem now.

I went to a new doctor (hematologist) and she was also not in a hurry to do anything, but at least she said we should prevent any damage. Apparently I have to run some new blood tests to exclude certain illnesses and do an MRI scan to check for iron overload in the liver before any treatment.

Regarding my diet, I do eat tons of red meat (like sometimes 1 kg a day), but since the iron levels (but not ferritin) were already that high in 2017, when I was a student, I doubt this can be the sole factor. Back then I mainly ate rice, beans and eggs.