"Maenner" is another good song, although it isn't my favorite on the album (which I'd give about a 4/5). About "Was soll das?", yes I understand the lyrics. I wouldn't say they were some of the best, but the arrangement is quite excellent, and the song is most definitely catchy. I heard taht his wife had died, along with his sister (correct me if I'm wrong), and that was what influenced him for "mensch" and some of his other songs, like "Bleibt alles Anders" (very emotional song and great video IMO: http://youtube.com/watch?v=oJd57NIW4XM).
And about Hammill, yes I heard they've worked together more than once, like you said Hammill translated one of Groenemeyer's albums, and Groenemeyer sang on "Fall," which I haven't heard yet....
Also, I've read that Groenemeyer worked with Lou Reed and Nick Cave
. That just has to be awesome.