I've only recently discovered these books and am having lots of fun catching up (i'm getting towards the end of Berlin Noir at the moment). I'm pretty impressed with the historical research, but there are some odd oversights, such as the anticip…
Gunther doesn't have an umlaut, so it IS more OO that ur, but not as long. Something along the lines of "fun" said with a northern accent.
Lehnhof - long e, that's what the h is there for.
Tauber - ou as in ouch!
Kuttner short U, similar to G…