"High Realism Tutorial" is on one of the back pages of the "Downloads/Silent Hunter 4/Gameplay mods" found on this forum site. Or, follow
THIS LINK. The latest version of the "AoB Calculator", which is a nice tool to use with the game, can me downloaded
HERE.
As Rockin Robbins noted, a result of torpedoes always missing to the stern of a target is the torpedo doors were not opened before you fired. Open each tube door before firing. They will stay open for a specific period of time, then close on their own after a firing, or exceeding the time limit. The Message Text Box will tell you which tube door you opened, or when you tell it to close.