Akela, If you can finish the torp tutorial with GW installed you are ready for the big show!
Sinking ships within this mod is meant to be harder but if you aim just right you can scupper them with a single shot.
Don't feel bad about it there are some older hands that are still finding out new things about this game even after more than 12 months playing it, myself especially included.
Don't worry too much about their "evasion" techniques. They may zigzag a bit but they are too slow to stop you catching em and killing em.
Gute Jagd!