I've been to Bochum many times and also needed the music (and common tongue) to survive. It's a pretty decent city for music. I can think of a few places where there might be sessions. There is definitely one at the Guinness Treff in Langendreer (suburb within Bochum)at least once a month on Sunday night (ask for Chris). Also try the the one Irish pub right in town near the Sudring (it used to be called Danny O'Brien's). There's another pub in the Daulhausen section of Bochum called the Irish Cottage...ask for Sven. There's a great pub in town called O'Neils. Jimmy behind the bar can tell you where more sessions are held. Jimmy's a character.
Essen, Dortmund, and especially Dusseldorf have a lot of Irish Pubs...again, ask Jimmy for advice.
Good luck.