Help with years of built up bio film

Hello! Long story short, I rent under a slumlord and my bathroom hasn’t been properly cleaned in ages. I was able to keep my own section kind of clean but now that the heat has kicked up we have a drain fly larvae issue. They thrive on eating the years of yellow biofilm built up in the corners of the showers. I’ve spent days scrubbing to no avail and I need something that will help dissolve the biofilm so these things stop having something to eat.

My landlord has been ignoring me lately so I’ve been hesitant to email to ask him for cleaners. I’m looking for quick at home remedies I could do myself rather than waiting on his crappy “contractor” to help.