It really depends on what you need 
UE4 (and game dev in general) is massive, and there are a lot of things going on. Some people settle with “just” learning to code, others to make effects. And so on.
So not sure if there is a crash course that will teach you everything.
But YouTube is your friend, and there are lots of great tutorials out there. I’d suggest following a tutorial series that shows how to make a game from scratch. Usually those give some insight into all the different areas.
Take a look at this for example, and pick a playlist that sounds interesting (maybe the “Mech Combat Game”)
Good luck on your journey!