How do namespaces work in C#?

Question

C++ / C#

Hello.
Namespace question.
for example the structure is:

using System;
namespace Life 
{
class CommonFeatures
  {
    //public void Main(){}
    public static void sayHello()
    {
      Console.WriteLine("I'm a creature...");
    }
  }
  ////////////////////////////
  namespace Peoples
  {
    class Man
    {
      // public void Main() {}
      public static void sayHello()
      {
        Console.WriteLine("Hello...");
      }
    }
  }
  ////////////////////////////
  namespace Animals
  {
    public class dog
    {
      public static void Main()
      {
        Life.Peoples.Man.sayHello();
        Life.CommonFeatures.sayHello();
        sayHello();
      }
      public static void sayHello()
      {
        Console.WriteLine("Gav, Gav...");
      }
    }
  }

}

why, if CommonFeatcher or Man write public and add Main, then the output is zero - just nothing happens?
Type entry point should be one?
How to refer to namespaces without constantly writing out the whole chain like ABCD ?

Answer 1

from what I understand:
you need to create an alias at the very beginning (which is inconvenient, IMHO)
can't you do it somehow directly in the context, inside a class or method?