I found Haskell Koans on GitHub. It was really good practice for me. I did it, but I couldn't solve Parser Combinator practice. I guess I'm stuck at basic list operation stuff. I tried many times, but failed after all (I couldn't satisfy return type "Parser String"). If you know the answer, please let me know.
Update: I solved "sequence of digits parser" practice by
P.many' P.anyChar but still struggle symbol parser.