structure your learning. He was a pentester and did it along the lines of: I am learning windows priv-esc now. I am learning linux priv-esc now. I am learning sqli now I am learning XSS now.
Then go over all the topics you wanna learn, becomming expert in them one-by-one. It can be a mess of 1000 things at once. Take lots of notes, save stuff for later, and focus on certain areas one by one.