[NoX]

Hey guys, what's up?
SH5 is my first subsim. actually, my first serious sim ever. I've done the "Tutorial", and I know how to navigate my submarine, and that's all.
I've started a new mission: sink 50k tons of carge in the British Waters, and then went to the open sea, and the game tells me to "(!) Patrol the designated area."
and to my questions:

1.how do I patrol an area? i've sailed around the marked point for a long, long time, and the game still tells me to partol the designated area.

2. in order to sink 50k tons of cargo, I should find Merchant ships first. how to do that?? I see little red squares on the map. and when I'm moving towards them the squares get brighter and move aswell, and till I get to those ships, they're long gone.
is there any special way to find ships and get to them before they run away?can u ambush merchant ships?

3.Lucky me, I've accidentally found about 6 or 8 ships sailing close to each other. there are 2 warships, and the rest are merchants. I got closer to them, and tried to attack them the way I learned in the tutorial. somehow, all of the 8 torpedos I shot at them, missed! what am I doing wrong? and what is TDC? please let me emphasize- in somepoint during this short battle, I was very, very close to one of the ships. so close I could see her fullsize with no periscope, we were parallel to each other, and my torpedo still missed... in short, how to hit with the torpedo??? it's not simple as it was in the tutorial level.

4.In this situation, when my sub and the merchant ship were so close and parallel, I've told one of my crew to deck the flak gun, well he did, but why he didn't he shoot at the ship which was so close to us? i've tried to shoot at it myself. but It seems like that bullets aren't even tickeling her! (assuming they hit her at all...). So, how do I use those deck guns? are they any useful?

5. I would love to get some general tips and other important stuff I should know from veteran boat hunters. and how do u engage 8 (or 6) ships?

I know I asked a lot here, I really hope u would take 5 minutes to read this and answer me, since this game seems awesome and its too bad I'm stuck in it for a long time now (I tried to find answers to my questions online before, without any success). thanks in advance, for any help.

P.S: is there some part of the game when u will encounter enemy submarine?