I am obviously out of my element a bit since I am way over here in the states but I thought I'd put my two cents in. I have had my
BMW for 6 years now and my father replaced the OBC about 5 years ago. To save money he bought the part from Germany so all the messages came stock in german. I found this website
http://home.online.no/~st-arhol/enge32obc.htm to be very useful in helping me. Obviously you probably know more German than I but I thought it may be of some help. It doesn't have all the messages but definitely a lot of the most essential ones. I still have a printed copy of this website from 5 years ago in my glovebox! Hope it helps!