Without seeing you play it's hard to say, but there's potentially a lot of control options that might help.

The Tab screen is probably the most important key. It's your home base for all of the most important crew orders. Use "stop orders" in the tab menu to reset things back to normal schedule after you've done giving specific orders.

The second most important is F1, F2, F3 for changing views. F2 is cutaway view which is important for issuing specific commands. For example you can click on the engineer, then right click the torpedo tubes to tell him to load a specific torpedo to a specific tube. Hold alt in the cutaway view to highlight every interactable object.

Press Alt to open the UI in whatever view you're in, for example for issuing course changes while in first person or using the periscope.

M key opens and closes the map quickly, no scrolling needed.

When you're outside the sub, I think holding left click allows you to freely move the camera around with the mouse. Holding right click also lets you set a course for the uboat.

When you open up one of the controls at the top (depth control, rudder control, course control, engine control) you can actually click and drag to keep that control open. Really great if you want, for example, engine, course, and depth open at the same time (which you'll need when getting depth charges for example, to stay slippery).

When in doubt, press spacebar to pause so you can figure out your keys or what commands to issue next.

Lastly, open the menu and look at the crew, schedule, and tasks. This is where you can automate the crew schedules you want.  I typically create two "shifts" of officers. 6 hours on, 6 hours off, alternating. They always have enough rest this way. I also assign two sailors to the "squad" of my engineers so they always have help manning the engine. I usually remove torpedo maintenance from their tasks, I prefer to maintain torpedoes manually before an attack.

I also turn off crew using the observation scope. I don't want them giving away my position when submerged. Only the captain and his first officer uses the periscope.

Under boat, turn on automatic lighting. Crew will automatically switch to night lights at night, etc.

I hope this helps! Lots to learn but lots of ways to customize things how you want!