End of the game?

[Gabbiani]

Hi, I'm new at the forum and at the game.
After reading some tutorials and practicing at the naval academy I left Kiel to my first patrol.
It turned to be a lucky one since I spoted an unguarded convoy.

Well, after few more patrols I noticed the dates were moving , so the question is?
The game is getting harder with more guarded convoys?
Do I have to change tactics?
the game ends in 1945?

thanks