WELCOME ABOARD!
As oppposed to even the best movies, the real world of submarines (and ships in general) is slow and boring by nature. I'm not sure if that's the problem your having, but even played at the simplest levels the SH series can be much less exciting to someone used to the excitement of just about any other kind of game.
While I agree with Rockin Robbins about playing the stock game first, I would recommend Operation Monsun, not because it adds more, but because it comes with a full set of playable training tutorials. Barring that, try the American side - it has its own training classes as well. Also you might go ahead and install one of the good sound mods, just because you'll get more immersion from hearing German voices in your u-boat.
All I can think of besides that is to ask lots of questions about anything and everything. We're always glad to help any way we can.