How to implement repository pattern for two or more entities

Question

I am trying to implement repository pattern for Web Api project and am confused while implementing the repository where two or more entities involved. What will the best approach for handling this case?

Generic Repository:

public interface IRepository<T>
{
    IEnumerable<T> Get();
    T GetById(int Id);
    int Save(T Object);
    bool Update(T Object);
    bool Delete(int Id);
}

Student Repository:

public class StudentRepository : IRepository<Student>
{
    private IDbConnection connection = new SqlConnection(ConfigurationManager.ConnectionStrings["ConnectionString"].ToString());
    public bool Delete(int Id)
    {
        int affectedRows;
        using (connection)
        {
            connection.Open();
            using (var trans = connection.BeginTransaction())
            {
                affectedRows = connection.Execute(StudentSql.Default.DELETE, new { Id = Id }, transaction: trans);
                trans.Commit();
            }
            return affectedRows > 0;
        }
    }

    public IEnumerable<Student> Get()
    {
        using (connection)
        {
            connection.Open();
            IEnumerable<Student> students = connection.Query<Student>(StudentSql.Default.SELECT);
            return students;
        }
    }

    public Student GetById(int Id)
    {
        using (connection)
        {
            connection.Open();
            Student student = connection.QueryFirstOrDefault<Student>(StudentSql.Default.SELECT_BY_ID, new { Id = Id });
            return student;
        }
    }

    public int Save(Student StudentModel)
    {
        int newRecordId;
        using (connection)
        {
            connection.Open();
            using (var trans = connection.BeginTransaction())
            {
                newRecordId = connection.QuerySingle<int>(StudentSql.Default.INSERT, new
                {
                    StudentModel.First_Name,
                    StudentModel.Last_Name,
                    StudentModel.Course_Id
                }, transaction : trans);

                trans.Commit();
            }
            return newRecordId;
        }
    }

    public bool Update(Student StudentModel)
    {
        int affectedRows;
        using (connection)
        {
            connection.Open();
            using (var trans = connection.BeginTransaction())
            {
                affectedRows = connection.Execute(StudentSql.Default.UPDATE, new
                {
                    StudentModel.Id,
                    StudentModel.First_Name,
                    StudentModel.Last_Name,
                    StudentModel.Course_Id
                }, transaction: trans);

                trans.Commit();
            }
            return affectedRows > 0;
        }
    }
}

Service:

IRepository<Student> repository;
    public StudentController(IRepository<Student> studentRepository)
    {
        repository = studentRepository;
        transformer = studentTransformer;
    }

    [HttpGet]
    [Route("api/v1/student")]
    public IHttpActionResult Get()
    {
        IEnumerable<Student> students = null;
        try
        {
            students = repository.Get();

            if (students.Count<Student>() > 0)
            {
                return Ok(students);
            }
            else
            {
                return StatusCode(HttpStatusCode.NoContent);
                //return Content(HttpStatusCode.NoContent, students);
            }
        }
        catch (Exception ex)
        {
            return InternalServerError(ex);
        }
    }

If i want Student along with course then i have to write a custom repository where it has to implement all the 5 methods in generic repository interface.

How to implement these methods? Can i write queries for the insertion of course and student inside the custom repository or i have to delegate this to individual repositories to get the insertion done?

Which approach is the best one?