In this context, a “party” or “group gathering” means, for example:
- more people in the apartment than those listed as tenants,
- loud music, shouting, or singing,
- drinking sessions that disturb neighbors,
- “pre-drinks”, after-parties, or celebrations that go beyond normal, quiet social visits,
- any event that creates significant noise or crowding in the apartment or building.
Basically: if it looks, sounds, or feels like a party, it is not allowed.