Update:
Weeks ago I couldn’t take it anymore (ha! the title!) and talked to the security guard (actually I was looking for the building manager but i ended up talking to this guy). I told him via google translate that the cunts downstairs wouldn’t stop making noise and shouting like schizophrenic asshole, and for some reason he said that also other people say that my “voice is too loud”. That’s weird, might be a funny translation for me being noisy too. Again, strange, I’m not really noisy at home. Anyway, he went up to the animal family’s door and since they wouldn’t open he shouted at them to shut the fuck up (I think).
Days later I left the house for CNY and apparently my neighbour talked to the building manager about noise and people moving furniture, supposedly because the conversation I half had with her. Someone put a note on the lift because of that, but the recurrent door slamming was not mentioned…
Moving forward some days… I realized that the next door idiots seem to have left lol. Maybe they were the ones who told someone that I was noise, maybe because the family downstairs making noises, maybe because of my two late night visits to their door, maybe because of both things. Whatever, I’m happy with them going quiet.
The animals downstairs seem to be overall quieter, but not totally. They still slam the door every now and then and the kids sometimes make noise, but there’s a small improvement, I think.