Victim of a landlord special: what can *I* do?

ill be mentioning some gross stuff, but none of it is visible in the images.

My building (52 apartments) was converted from an office building about 6 years ago, and it's becoming more and more clear to those of us who were here since the start that many corners were cut during construction.

Most notable is the bathroom, which i frequently come home to smelling like an actual sewer. image 1 is the siphon that is under my bathroom sink, which i tried to replace with a cup/bottle siphon (image 3), but it doesnt fit due to how high up the plumbing in the wall is (at least with the ones i can pick up ready to be assembled at the home improvement store).

image 2 is the setup in my shower, recently flushed with plenty of hot water because there was half dissolved toilet paper in there again.

The sewer problem is known to the owners of the building, but theyve been dragging their feet (repair people have come to assess the situation on multiple occasions but the issue is not being resolved) and frankly i just want to stop the gas and sewage from entering my apartment.

The most straightforward thing would be to plug everything up as airtight as possible when not in use, but i assume waterlocks are used in plumbing setups for a reason and i don't want to exacerbate the problem, especially for my neighbors. Any advice on how to stop the smell in a more permanent way (since flushing with water and sometimes vinegar only helps temporarily) is super welcome