So guys, do you think I should learn one functional programming language and if so should it be haskell?

No, you said you were going to learn Kotlin, so stick to that and learn it well.

But if you want to learn Haskell, or F# or Ocaml, or Elixir then be my mofocking guest. I recommend Elixir, although all of them are great.

But yeah, stick to the tool that will let you build what you want man, trust me, language jumping is gonna hurt you more than help at an early stage:

Source: fuckd me up pretty bad at first.

@AleCx04 Thanks i will wait for like 6 months.