this idiot cat

Last night I got back to the borrowed flat and found this idiot cat that used to live in said flat and thinks it still does waiting for me on the borrowed bed where I’m sleeping; later, retiring, I found that said cat had peed on said bed, like, with authority, and volume.
I spent much of the night not sleeping but disassembling and washing, and when I got up to resume that work this morning, the same cat was waiting for me in the living room in spite of having been thrown thoroughly out.
Now I have posted signs on all the points of feline ingress I can divine reading MIKE IF YOU COME IN HERE AGAIN I WILL DROWN YOU and the same again, just in case, in German.