I would highly recommend Udemy courses (wait till they go on sale though). Some of them are very long and detailed and should give you a much better idea of the engine works.
Here’s one course by Ben Tristem which I’m sure you can learn a lot from (although there is more emphasis on C++).
https://www.udemy.com/unrealcourse/learn/v4/overview
And this course by Chris Murphy has more Blueprint:
https://www.udemy.com/unreale4/learn/v4/overview