hacer una suma pidiendole al usuario que ingrese los numeros desde otro clase

void Main()
{
    Console.WriteLine("Welcome to this calculator!");
    Console.WriteLine("It can add, subtract, multiply and divide whole numbers from 0 to 50");
    Start();
}

public void Start()
{
    bool isFinished = false;
    while (!isFinished)
    {
        string numInput1 = GetInput("Type in your first number (or 'Q' to quit):");
        if (numInput1.ToUpper() =="Q")
        {
            isFinished = true;
            continue;
        }
        string numInput2 = GetInput("Type in your second number (or 'Q' to quit):");
        if (numInput2.ToUpper() =="Q")
        {
            isFinished = true;
            continue;
        }
        double result = 0;
        string op = GetInput("What do you want to do? (+, -, *, /)");
        try
        {
            double num1 = double.Parse(numInput1);
            double num2