Сещам се за тази задача..

пускам ти моето решение 

https://pastebin.com/UqmN5K7h

The main-idea behind this exercise is to push the student to start using private helper-methods, because even if your code is 500 lines or more you can still handle the information when everything is sliced up into smaller pieces of code. If all of the code is placed into one single method, then debugging becomes a nightmare.

Best,

using System;
using System.Linq;
using System.Collections.Generic;

namespace softuniCoursePlanning
{
    class Program
    {
        static void Main(string[] args)
        {
            List<string> courseSchedule = Console.ReadLine().Split(", ").ToList();
            List<string> filter = courseSchedule.FindAll(course => course == "Data Types");
            string command = Console.ReadLine();

            while (command != "course start")
            {
                string[] operation = command.Split(':');
                switch (operation[0])
                {
                    case "Add":
                        AddOperator(operation[1], courseSchedule); break;
                    case "Insert":
                        InsertOperator(operation[1], int.Parse(operation[2]), courseSchedule); break;
                    case "Remove":
                        RemoveOperator(operation[1], courseSchedule); break;
                    case "Exercise":
                        ExerciseOperator(operation[1], courseSchedule); break;
                    case "Swap":
                        SwapOperator(operation[1], operation[2], courseSchedule); break;
                    default:
                        break;
                }
                command = Console.ReadLine();
            }
            int counter = 1;

            foreach (var item in courseSchedule)
            {
                Console.WriteLine($"{counter}.{item}");
                counter++;
            }
        }

        static List<string> AddOperator(string title, List<string> courseSchedule)
        {
            bool lessonExist = courseSchedule.Exists(course => course == title);
            if (lessonExist)
            {
                return courseSchedule;
            }
            courseSchedule.Add(title);
            return courseSchedule;
        }

        static List<string> InsertOperator(string title, int index, List<string> courseSchedule)
        {
            bool lessonExist = courseSchedule.Exists(course => course == title);
            if (lessonExist)
            {
                return courseSchedule;
            }
            courseSchedule.Insert(index, title);
            return courseSchedule;
        }

        static List<string> RemoveOperator(string title, List<string> courseSchedule)
        {
            bool courseExist = courseSchedule.Exists(course => course == title);
            bool exerciseExist = courseSchedule.Exists(exercise => exercise == title + "-Exercise");

            if (courseExist)
            {
                courseSchedule.Remove(title);
            }
            if (exerciseExist)
            {
                courseSchedule.Remove(title + "-Exercise");
            }
            return courseSchedule;
        }

        static List<string> ExerciseOperator(string title, List<string> courseSchedule)
        {
            bool courseExist = courseSchedule.Exists(course => course == title);
            bool exerciseExist = courseSchedule.Exists(course => course == title + "-Exercise");
            int courseIndex = courseSchedule.FindIndex(course => course == title);
            int exerciseIndex = courseIndex + 1;
            if (courseExist && exerciseExist == false)
            {
                courseSchedule.Insert(exerciseIndex, title + "-Exercise");
            }
            else if (courseExist == false)
            {
                courseSchedule.Add(title);
                courseSchedule.Add(title + "-Exercise");
            }
            return courseSchedule;
        }

        static List<string> SwapOperator(string title1, string title2, List<string> courseSchedule)
        {
            bool course1Exist = courseSchedule.Exists(course => course == title1);
            bool course2Exist = courseSchedule.Exists(course => course == title2);
            bool exercise1Exist = courseSchedule.Exists(course => course == title1 + "-Exercise");
            bool exercise2Exist = courseSchedule.Exists(course => course == title2 + "-Exercise");
            int course1Index = courseSchedule.FindIndex(course => course == title1);
            int course2Index = courseSchedule.FindIndex(course => course == title2);
            int exercise1Index = courseSchedule.FindIndex(course => course == title1 + "-Exercise");
            int exercise2Index = courseSchedule.FindIndex(course => course == title2 + "-Exercise");

            if (course1Exist && course2Exist)
            {
                string oldElement = courseSchedule[course1Index];
                courseSchedule[course1Index] = courseSchedule[course2Index];
                courseSchedule[course2Index] = oldElement;
                course1Index = courseSchedule.FindIndex(course => course == title1);
                course2Index = courseSchedule.FindIndex(course => course == title2);

                if (exercise1Exist && exercise2Exist)
                {
                    string oldElement2 = courseSchedule[exercise1Index];
                    courseSchedule[exercise1Index] = courseSchedule[exercise2Index];
                    courseSchedule[exercise2Index] = oldElement2;
                }
                else if (exercise1Exist)
                {
                    string oldElement4 = courseSchedule[exercise1Index];
                    courseSchedule.Remove(oldElement4);
                    courseSchedule.Insert(course1Index + 1, oldElement4);
                }
                else if (exercise2Exist)
                {
                    string oldElement5 = courseSchedule[exercise2Index];
                    courseSchedule.Remove(oldElement5);
                    courseSchedule.Insert(course2Index + 1, oldElement5);
                }

            }

            return courseSchedule;
        }
    }
}