Well, you seem to be doing quite Ok.....BUT...remember its early days and things get more trickier as the war progresses
SMF are indeed slow, medium, fast. You can vary speeds depending on each situation as it is required. Some eels only have a slow setting though.
Transfers can be fun, but bear in mind that some flotilla's only offer certain types of boats.
Yes shallow water is not a submarines best friend. As the ware progresses you will soon learn that depth and stealth are the U boat's best friend.
Enjoy these easy days you are experiencing