Решение:

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

namespace Notifications
{
    class Program
    {
        static void Main(string[] args)
        {

            var n = int.Parse(Console.ReadLine());
            for (int i = 0; i < n; i++)
            {
                ReadAndProcessMessage();
                Console.WriteLine();
            }

        }
        static void ReadAndProcessMessage()
        {

            string messageType = Console.ReadLine();
            if (messageType == "success")
            {
                string operation = Console.ReadLine();
                string message = Console.ReadLine();

                ShowSuccessMessage(operation, message);

            }
            else if (messageType == "warning")
            {
                string warningmessage = Console.ReadLine();

                ShowWarningMessage(warningmessage);
            }
            else if (messageType == "error")
            {
                string operation = Console.ReadLine();
                string errormessage = Console.ReadLine();
                int errorCode = int.Parse(Console.ReadLine());

                ShowErrorMessage(operation, errormessage, errorCode);
            }

        }
        static void ShowSuccessMessage(string operation, string message)
        {

            string head = "Successfully executed " + operation + ".";

            Console.WriteLine(head);
            Console.WriteLine(new string('=', head.Length));
            Console.WriteLine("{0}.", message);

        }
        static void ShowWarningMessage(string warningmessage)
        {

            string head = "Warning: " + warningmessage + ".";
            Console.WriteLine(head);
            Console.WriteLine(new string('=', head.Length));

        }
        static void ShowErrorMessage(string operation, string errormessage, int errorCode)
        {

            string head = "Error: Failed to execute " + operation + ".";
            Console.WriteLine(head);
            Console.WriteLine(new string('=', head.Length));
            Console.WriteLine("Reason: {0}.", errormessage);
            Console.WriteLine("Error code: {0}.", errorCode);

        }
    }
}