Please give me solution as sharp as because i need it ,,please

i have assignmentremark, assignment and assignmentsubmission table and there is teacher and student is also a diffrent table

now as a teacher i upload a assignment and that assignment student can submited on diffrent submissioncontroller and that give mark of that subitedassignment by teacher on assignment remark controller

so how i can merge this three controller in my proect to give best view in mvc.net step by step with example in controller

This is My AssignmentRemark Model code:

namespace VCS_MVC_Project1.Models
{
    public class AssignmentRemark
    {
        [Required]
        public int ID { get; set; }
        [Required]
        public int StudentId { get; set; }
        public Student Student { get; set; }
        [Required]
        public int TeacherId { get; set; }
        public Teacher Teacher { get; set; }
        [Required]
        public int Marks { get; set; }
        [Required]
        public int AssignmentId { get; set; }
        public Assignment Asssignment { get; set; }
    }
}

This is Assignment model Code:

namespace VCS_MVC_Project1.Models
{
    public class Assignment
    {
        [Required]
        public int ID { get; set; }

        [Required]

        public string Name { get; set; }

        [Required]
        [StringLength(300)]
        public string Description { get; set; }

        [Required]
        [Display(Name = "Attechment")]
        public string Attechment { get; set; }

        [Required]
        [DataType(DataType.Date)]
        [DisplayFormat(DataFormatString = "{0:dd/MM/yyyy}", ApplyFormatInEditMode = true)]
        [Display(Name = "Due Date")]
        public DateTime Due_date { get; set; }


        public Teacher Teacher { get; set; }
    }
}

this is the AssignmentSubmission modelCode:

namespace VCS_MVC_Project1.Models
{
    public class AssignmentSubmission
    {
        [Required]
        public int ID { get; set; }

        [Required]
        [Display(Name = "Files")]
        public string Files { get; set; }

        [Required]
        [DataType(DataType.Date)]
        [DisplayFormat(DataFormatString = "{0:dd/MM/yyyy}", ApplyFormatInEditMode = true)]
        [Display(Name = "Date")]
        public DateTime Date { get; set; }

        public Student Student { get; set; }

        [Required]
        [Display(Name = "Student Name ")]
        public int StudentId { get; set; }

        public Assignment Asssignment { get; set; }

        [Required]
        [Display(Name = "Assignment Name")]
        public int AssignmentId { get; set; }
    }
}

give the solution for quetion asked in first

What are the relation between the three classes AssignmentRemark, Assignment and AssignmentSubmission?

Assignment Submission and assignment Remark both are relation with  foriegn key of Assignment table primary key ID 

Use the following code to edit the student Image.

First save the image from the FileUpload in Edit Action method and assigned saved path to the Image property.

[HttpPost]
[ValidateAntiForgeryToken]
public ActionResult Edit([Bind(Include = "ID,Name,Dob,EmailID,Password,PhoneNO,Image,CityId,ZipCode,Address,Gender")] Student student, HttpPostedFileBase image)
{
    if (ModelState.IsValid)
    {
        string hashedPassword = BCrypt.Net.BCrypt.HashPassword(student.Password);
        student.Password = hashedPassword;
        var fileName = Path.GetFileName(image.FileName);
        image.SaveAs(Path.Combine(Server.MapPath("~/S_Images/" + image.FileName)));
        student.Image = fileName;
        db.Entry(student).State = EntityState.Modified;
        db.SaveChanges();
        return RedirectToAction("Index");
    }
    ViewBag.CountryId = new SelectList(db.Countries, "ID", "CountryName", student.City.State.CountryID);
    ViewBag.StateId = new SelectList(db.Cities, "ID", "StateName", student.City.StateId);
    ViewBag.CityId = new SelectList(db.Cities, "ID", "CityName", student.CityId);
    return View(student);
}