There’s a class on Coursera by Dr Barbara Oakley https://www.coursera.org/learn/learning-how-to-learn?
It gives you a basic model for skill retention. You should modify the style to what works for you. I’ve successfully retained what I’ve revised and practiced
Paradoxically, you're telling to learn a course that tells you right way to learn something.
So until then you don't know the right way to learn to learn the course you suggested.
xD nah I'm kidding. It's a good one.