Your bathtub drains directly into a concrete sump pit; not "the wall" as such but a pit constructed for this purpose. In the US and Canada, open sumps are used only for groundwater, like from drains that prevent basement floording. It kinda looks like someone wanted to put a bathroom into a basement, cheap, and came up with the horrific but clever idea to just put the tub over an existing groundwater sump.
First thing you should do is figure out what else drains into it. If it's just the tub and a nearby sink, you'd call it a "grey" water sump. By US and Canada code, this is really wrong. There are parts of the world with, well, different plumbing codes so I can't say if this is crazy wrong where you are. If it's only greywater involved, it's not necessarily an immediate health hazard.
If a toilet drains into it, it's "black" water, your apartment must reek something awful, and really I think you should consider the place unlivable. I can't imagine it's acceptable anywhere on the planet to live in a place with an open sewer pit.
There is no "fix" other than to gut the bathroom and, at significant expense and disruption, dig up the floor and install a proper closed sump. Your landlord will already have considered this and you can see he opted as he did.
Note added later: is there any other access into that pit? a hatch or door or something? That plastic sump pump is not going to last forever, and it surely isn't going to be removed and replaced via the bathtub drain hole. If there's no other access, then I take back the "clever" part of my comment above; this is just horrific.