Identify the fundamental components and work on them.
When you improve your understanding of the basics, you will notice the subtleties of complex ideas more easily. Your level of clarity around advanced concepts will skyrocket because you will be able to connect simple concepts in unique ways. Everything will make much more sense than before.
Take any skill or subject area that you wish to improve on.
It can be anything related to your professional or personal life.
List all the fundamental components that make up that skill or subject.
This list does not have to be exhaustive. It can just be a free-flowing stream of consciousness.
Now pick any one of those components and spend 30 minutes learning about it.
Write down everything you know about that component and explain each concept of it. Try to understand how it fits into the bigger picture. You have to be brutally honest with yourself. If you don't know something, admit it. And commit to learning these unknown skills as soon as possible rather than glossing over them.