Thanks again to all you guys on this forum for your help!
After some practice sessions with destroyers I started career mode again, this time with GWX and SH3 Commander (real ship names, no fatigue, stop TC on enemy contact). Flotilla 2, UBoot VIIb.
Set realism to 80% (still need help from the WO to ID those merchants), spent some of my precious renown on officer skills, and - for the second patrol - on a KDG hydrophone. Had a great time, enemy warships far enough, some minor cargo and two Large Merchants sailing my way.
Ended 2nd patrol with 6 ships sunk (34k t) after only 8 days (out of front torpedoes)
I play the downloaded version (amazon, not steam), on Win7 64bit. Tried to install the hi-res patch but no effect, it still sends 1024x768 to my monitor, hm. Good enough, though.
Next patrol, I'm going to shoot down those planes
OLt zS Helmut