I have been learning F# for a while now, and while the functional side that is pushed heavily is a joy to use, anything that touches the 'outside world' is going to have way more resources for C# as far as libraries, official documentation, general information including tutorials etc. You will need to understand and work with those.
So you really do need to understand C# syntax and semantics. Additionally there are a few concepts that seem the same in each language but have different implementations and are not compatible (async vs tasks, records) so there is additional stuff to know about when mentally translating between C# and F#.
I really want to love F# but keep banging my head against the wall. Elixir while not being typed yet and not being as general purpose at least allows me to be productive with it's outstanding documentation, abundance of tutorials and books on both the core language and domain specific applications. It is also very easy to mentally translate erlang to elixir and vice versa in the very few occasions needed.