I would not worry about dynamic typing, because if it scares you, you can still code everything statically (
var my_var would be dynamic, but
var my_var:float is statically typed and works as you would expect).
For C# you will need to code in an external editor, which makes the workflow a little more tedious (extra tedious for beginners). Mostly for this reason
I recommend using GDScript, which you can use inside Godot. Script functions are calling internal C++ methods anyway, which means that GDScript might be
in most cases slightly more performant than C# (but that's a bit of my perspective).
(Note: Most performant would be C/C++ itself, but that's also the "most difficult language".)
For me the only downside of using GDScript might be that no non-gaming company (like the guys who make banking/financial systems) will care much that you have a knowledge of it, even though it's based off python. (However this does not apply if you have enough experience in other languages as well - at that point, every little experience counts.)
If you're interested,
you can read more about Godot's scripting languages in the documentation. 
(You can actually use all of them throughout your project. Just don't use VisualScript, it won't be supported in Godot 4.x)