I moved from reaper to cubase and I’ll tell you how I learned cubase quickly: start your next project in cubase and have the operation manual in an adjacent screen.
Steinberg did a fantastic job with the manual and I find the explanations easy to follow for the most part. Once you hit a roadblock, google the question or YouTube it (for things like score editor, variaudio, time stretching, etc). For tips and tricks ask the forum. You might not work on a project that hits every major feature of cubase but you’ll get very comfortable with it and it beats reading books by a country mile.
Now I feel like a fish out of water when I open reaper. 