How to learn quicker and retain what you learn?

Reproduce whatever you learn. Test yourself on it.

Explain it in your own words Reproduction solidifies it in your mind.

Have I missed anything?

Question

How to learn quicker and retain what you learn?

Reproduce whatever you learn. Test yourself on it.

Explain it in your own words Reproduction solidifies it in your mind.

Have I missed anything?

Answer

You missed the fact that in your example quick is an adverb describing the verb learn and as such should be "How to learn more quickly..."