Youtube videos with helpful introduction to the science of learning. However, please remember that watching these videos will not help you improve; following the actionable plans discussed in the videos will.
Helpful starting place for research findings on learning.
Mindset by Carol Dweck
How to Write a Lot by Paul Silva
Fluent Forever by Gabriel Wyner
Not all self-help books are alike. These books incorporate empirical studies into a clear, cohesive account of how to learn effectively and why it works.
You can find free courses from reputable instructors and institutions. However, you will not know what to do with the information if you don't know how to process and encode that information in a useful way. If you struggle to learn independently, contact me for a FREE consulation or consider taking my course on effective learning.