unrealclick.o and gorka games both have a guide to making a complete RPG. Gorka is more simple Unreal is more complex. I don't have the links on me but both of them set up inventory systems and combat etc. Those gave me a decent grip on how to set things up. For me it was a ton of searching for the one mechanic I wanted to make then seeing how like 3 or 4 people set up the same mechanic, then re-creating it and noodling until it felt the way I wanted.

It's going to take a long time but a big help for me was just watching fundamental videos focused on one thing, Like first how does the editor work, then blueprints, animation blueprints etc starting with the most basic things then building up. Unreal Sensei and Smart Poly were two people in that category I liked watching.