To be honest, when I tried using it forever ago I got lost and gave up. I forced myself to use it because I liked the feature set, but moving over from FL was very difficult for me.
It took time, but I’ve figured it out enough to where I can’t imagine using anything else.
Reaper is very menu heavy, but has a good amount of keys bound to actions. Check the key bindings list and try to memorize them, much like you probably have done for other things given your setup.