Glad you're having a win.
Have you modded the game yet, or are you still using stock?
Have you started your second patrol yet? Once you leave wilhelmshaven (hope i spelt that right) and head for the open ocean you'll find some deeper water. Depth is repreented on the chart (navigation map) by colour, so the darker the shade of blue the deeper the ocean.
When you u get to some deeper water you'll soon encounter a bug that'll kill your sub before you know whats hit ya! When diving at slow speed your sub will not level out at your ordered depth and you will not be able to surface till you crank the speed right up. Gets pretty hairy when you're being hunted by dd's but once you know what to expect it is managable.
Unfortunately ordered controll of your guns is broken. If you select a deck gun target (by pressing space while in bino view) the crew'll just keep on firing till they're outa targets or outta amo! The simple (and fun) fix for this is to just man the gun yourself, otherwise you gotta order 'secure the deck gun' to stop them.
Fortunately the grouse crew of modders on this forum have real fixes for these problems. It is a good idea to get aquainted with the stock game first though (IMO).