It has been said that one of the best ways to learn something is to teach what you have learned to someone else.
That said, writing is also a form of teaching, that is, you write what you want your student to learn.
Through that, we can say that one way to learn something better is to write about it.
But if you’re uncomfortable other people seeing what you’ve written then you can make your writing private instead. When you write, you write for your imaginary student. Go on. No need to worry since no one else will be judging you.
As long as you can comprehend what you’ve written. When the time comes you read it again, then it has served its purpose, not only have you learned better by writing about it — you also provided yourself with a handy reviewer.
So what are you waiting for? Want to learn something effectively? Then, read something about a topic which interests you; afterwards, write what you learned as if you’re teaching it to someone else.
After a few days, weeks, or even months, read again what you have written to refresh your mind and congratulate yourself, for you are both a learner and a writer.