Welcome aboard Alfapiomega.
As for you question on Learning Curve, I'd say run a few the single missions with the different U-boats offered. It's on good way to get the feel of how the subs handle out on the high seas and with the enemy ships you will possibly encounter. It'll give you a good feel on firing torpedoes in combat and under pressure...... more so IMHO than the Naval Academy does. That goes for both manual and the "automatic" firing of torpedoes. They'll also help you in getting away from the Escorts that will hunt you down.
Good luck and sink em all!