Definitely C#. You’ll find tons more resources. F# is fantastic, but it’s not a good *first* programming language.

A lot of what you’ll learn when you first learn programming is going to be applicable in any language though. Once you’re comfortable with C#, and can understand the difference between imperative, object-oriented, and functional programming, you’ll be in a good place to check out F# (or any other language, really).

Good luck with your learning!