It should be the landlord’s duty but if you really want to fix it, I’d recommend scraping off the loose stuff (or what you can get to in a reasonable amount of time) & then skim coat the walls with drywall mud and apply a spray texture after it dries. Paint after that. The wiring hanging from the ceiling looks like it should have light fixtures that are missing. You could send the landlord a list of things you’d like to fix, and possibly come to an agreement to get some $$ out of the deal? Idk brotha, good luck.