Im a beginner

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Hangman
{
    class Program
    {
        static void Main(string[] args)
        {
            string CorrectWord = "mamamia";
            String HiddenWord = "";
            int lose = 0;

            
            for (int i = 0; i<CorrectWord.Length; i++)
            {
                HiddenWord += "_";
            }

            for (int i = 0; i!=CorrectWord.Length;)
            {
            Console.WriteLine(HiddenWord);
            Console.WriteLine(" Guess a letter");

            char guess = Convert.ToChar(Console.ReadLine());
            int index = CorrectWord.IndexOf(guess);

            if (index != -1)
            {
                HiddenWord = HiddenWord.Remove(index, 1).Insert(index, guess.ToString());
                    i++;
                
            }
            else if(index == -1)
            {
                lose++;
            }

            }
        }
    }
}