Hey man....sounds like my first Aces of the Deep exiperance about 20 years ago....(holy crap Im getting old!!). Anyway...Unlike SH3...SH5 stock is a bit of a joke around these parts...good graphics...but honestly very very buggy...even after two patches.
My first bit of advise....take it slow!!! and dont quit!! You will be frustrated a little bit...but thats a bit of growing pains of learing to Sim.
Time Compression can be a double edge scharwtz in SH5. I never ever get above 128 TC when I'm within range of enemy aircraft...never above 256 in enemy waters...and never above 512 (only in safe waters) ever. If you go to max TC and the game starts lagging...its a sign that the game Spawned an Enemy close to your position and you could be F'ed. What I'm assuming is your TC is killing you by not stopping in time for you to evade.....but i'm not knowledgeable enought on SH5 TC to give you a clear anwser.
MODS...or Modifications. This game almost requires them to be playable and to quell frustrations of an unfinished product and to extend the longevity and playability of the game. Check out the MODS section on how to start MODing your game. I was a computer dummy and I figured it out starting with SH3.
http://www.subsim.com/radioroom/showthread.php?t=190656
Half the fun of this game is mastering how to fight your boat...and some times you win...some times you dont....I'd try a bit of trail and error. There is a lot of good reading on this sight on how to master the craft of being a Stealthy Captain. But it takes a bit of time and commitment but its worth it. But the bottom line again is...Stock is broken...even with 2 patches!