Drain problems at my apartment.

The drain in my shower has been cleaned out by my landlord, but it's still slow, and recently when I have water draining in the sink, some of it comes up in the shower with gunk and doesn't drain back all that quickly at all.

I then plunge it, and huge black gunk pieces with very little smell and the consistency of jello come up from the drain and swirl around in the water, and I scoop them up and put them in a plastic bag to throw out.

I wonder if I should get my landlord on this again, or if I should just keep plunging the shower drain myself.

I really have no idea what could be causing this – soap scum? shaving cream scum?.  I’m not putting anything unusual down my drains.

He's already looked at it once too and cleaned out some draintrap, and things worked fine for a while.