fed up with these challenges

Hi there,

I think the issue here is where the code was added for the second set of objectives - it should be under Teacher.cs. It looks like you've deleted the contents of Course.cs and placed a Teacher class there instead. Generally the challenges will build on what you've already done - you usually don't want to delete something you did for a previous step unless it specifically tells you to. It can be sneaky, but keep an eye out for when an objective specifies a file - sometimes there are multiple tabs and you need to switch.

You've got the right idea with the code, though - it just needs to be in the right file, with the initial code and the previous step intact. Should look something like:

Course.cs (first step)

namespace Treehouse.CodeChallenges
{
    public class Course
    {
        public int Id { get; set; }
        public string Title { get; set; }
        public string Description { get; set; }
        public int Length { get; set; }
        public int TeacherId { get; set; }
        public Teacher Teacher {get; set; }
    }
}

Teacher.cs (second step)

using System.Collections.Generic;

namespace Treehouse.CodeChallenges
{
    public class Teacher
    {
        public int Id { get; set; }
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public ICollection<Course> Courses {get; set; }

        public Teacher() {
            Courses = new List<Course>();
        }
    }
}

Hope this helps!