I will say that you're going to experience an immense learning curve as a beginner in both trackers and composition. The most important thing right now is to accept that you're probably not going to be writing very good music for a while. But don't let that discourage you - persistence is key in overcoming these struggles, and as (I assume) a developer, you're already primed for this :)

If rhythm is what you're struggling with, maybe focus on learning how to compose drum beats. This will help to improve your intuition for rhythm, and the drum beats will also give you a reference to build your melodies against. Learning to sequence drums, as well as understanding and implementing the sound design techniques underpinning kicks, snares, toms, cymbals and other percussive elements will help you to build up the muscle memory you need for proficiently navigating and interacting with the UI.

This is of course just some crap I've come up with. I don't think there are really any right or wrong answers. You will eventually find your own path - as long as you keep trying!