[PL] translation of functions lesson (#303)
[PL] translation of functions lesson (#303)

* part of functions translation

* private functions translation

* [PL] translation of functions lesson

* fix paths

* Fix typos

ElixirVietnam/elixir-school,yuriibodarev/elixir-school,nscyclone/elixir-school,doomspork/elixir_school,psantos10/elixir-school,holsky/elixir-school,nscyclone/elixir-school,doomspork/elixir_school,nscyclone/elixir-school,huydx/elixir-school,huydx/elixir-school,yuriibodarev/elixir-school,ElixirVietnam/elixir-school,psantos10/elixir-school,holsky/elixir-school,erickgnavar/elixir-school,erickgnavar/elixir-school,huydx/elixir-school,erickgnavar/elixir-school,doomspork/elixir-school,doomspork/elixir-school,doomspork/elixir_school,doomspork/elixir-school,holsky/elixir-school,nscyclone/elixir-school,ElixirVietnam/elixir-school,psantos10/elixir-school,yuriibodarev/elixir-school