Streams, Enums and the functional idioms can be hard to memorize. My advice is to not worry too much about memorizing every function, but learn one everytime you solve a new problem. When I was learning F#, I started with map, reduce and filter only. Then, everytime i solve a problem, I would consult the list of functions, and see if any of them applied. Sometimes I’d miss out things I could do, but that’s ok.
Now when I am learning Elixir, I do the same thing. Also, you can always come here and ask for improvements 
