Here's an idea that a harbor master suggested to me once. I took his advice and it made me a better boat handler.
Wait for a calm windless day. Get one friend to stand by with a boat hook on the dock
to give you confidence (and push and pull you as you learn to keep from hitting anything.)
And, then just practice going in and out of that slip over and over again, until you start to get the hang of it. No pressure, no guests on board. No wind
(after you get hang of no wind, pick a windy day and do the same thing).
Just you learning
about your boat and how it handles. You'll like the way it feels when you to start to master it.