The best way to execute copy constructor using .Copy?

So I need help executing this copy constructor in my object oriented program. The result should be to copy string 1: Hello World into string 2: This is a test.

In my .h file:

void Copy(MyString& one);
 

In my .cpp file:

void MyString::Copy(MyString& one)
 {
    one = String;
 }
 

In my main.cpp file:

String1.Print();
 cout  << endl;
 String2.Print();
 cout  << endl;      
 String2.Copy(String1);      
 String1.Print();       
 cout  << endl;
 String2.Print();
 cout  << endl;
 

The output:

Hello World
 This is a test
 is a test
 This is a test
 

It should be:

Hello World
 This is a test
 Hello World
 Hello World
 

Please explain to me what am I doing wrong?

Here is my entire .cpp file:

MyString::MyString()
 
 {
 
 char temp[] = "Hello World";
 
         int counter(0);
         while(temp[counter] != '') {
                 counter++;
         }
         Size = counter;
         String = new char [Size];
         for(int i=0; i < Size; i++)
                 String[i] = temp[i];
 
 }
 
 MyString::MyString(char *message)
 
 {
 
       int counter(0);
 
        while(message[counter] != '') {
 
       counter++;
 
    }
 
         Size = counter;
 
         String = new char [Size];
 
 
          for(int i=0; i < Size; i++)
 
            String[i] = message[i];
 
 }
 
 MyString::~MyString()
 
 {
 
         delete [] String;
 
 }
 
 int MyString::Length()
 
 {
               int counter(0);
 
               while(String[counter] != '')
              {
                      counter ++;
              }
 
                 return (counter);
 }
 
 void MyString:: Set(int index, char b)
 
 {
 
          if(String[index] == '')
 
           {
                    exit(0);
           }
 
          else
 
         {
 
                    String[index] = b;
           }
 
 
 }
 
 void MyString::Copy(MyString& one)
 
 {
 
         one = String;
 
 
 }
 
 char MyString:: Get(int i)
 {
 
              if( String[i] == '')
              {
                      exit(1);
              }
             else
             {
 
                     return String[i];
 
             }
 }
 
 
 
 void MyString::Print()
 
 {
 
         for(int i=0; i < Size; i++)
 
             cout << String[i];
 
              cout << endl;
 
 
 }
 

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