Does anyone know how I fix a "A namespace cannot direc.." error?

I’m getting this error that I haven’t used Unity enough to know how to fix:

I take it the compiler is yelling at me because I can’t declare a variable directly inside the namespace. Can anyone tell me how to resolve this difficulty?

You can’t write JS script in C# script. This tutorial seems be old.
I would recommend you to go into some latest tutorials. JS (and Monodevelop aswell) are deprecrated.
Transition from JS to C# is pretty fast and easy.

Could I ask for a link to get me started on that transition?

… I got Visual Studio installed . I would like to how I can communicate to Unity that I want to use that instead of MonoDevelop.

Visual studio intergration: Unity - Manual: Visual Studio C# integration
For learning C# with unity official tutorials are just good Learn
C# is much more popular than JS, so you can easily find any other tutorials

Thank you!