One other thing you can try if you're new or coming back to DW, open your mission editor and create a very basic mission of just you in the sub you want to play. Start the mission and flog the snot out of your boat.
Get to where you have a really good "feel" for how your boat operates. Find your preferred numbers for things like going to PD, raising the radio and ESM masts, etc.
Run at different depths and speeds. Where do you cavitate? When does your sonar wash out? When are you leaving a wake near PD? How quickly can you change depth at a given speed?
Then change the mission to include a surface contact and practice tracking them. Try changing your ENVIRONMENTAL CONDITIONS as you practice tracking your contact.
Then, add a sub and track both contacts.
Start a new mission that's just you vs a patrol plane and a helo. Set the ROE to "peacetime" at first, you'll know if they can track you when you replay the mission. Then change it so they'll shoot at you.
Last, practice launching weps at your contacts.
Building up your skill over time is actually very realistic. IRL, crews will practice for weeks prior to a deployment.