"Functional programming" doesn't mean breaking code into smaller methods. Functional programming is a pretty different way to think about software (compared to writing a list of instructions to be followed).

I did a little googling and came up with this: https://wiki.haskell.org/Functional_programming . Maybe that helps?

I don't have much experience with functional programming myself, but I did enjoy reading a cute little book called The Little Schemer: https://mitpress.mit.edu/books/little-schemer . I haven't had a chance to read the rest of the series.