If you don't understand a compiler error, google it: Compiler Error CS5001 | Microsoft Docs
Quote:Program does not contain a static 'Main' method suitable for an entry point
Why does it throw it on your code?
Simpel: how many static Main methods do you have? If it's more than one it has no idea which one it should be calling.
And the one and only Main method needs to be inside a class as C# has no concept of "global" methods, variables, or properties.