Making my 2d character's arm follow the mouse, scrpit not working, please help :c

Hey! So I followed brackeys tutorial and laso used the unity's 2d-game sample. The thing is that I want to make the arm rotate acording to the mouse's position. hovever it's not working and just makes the arm fall down and ''dingle'' for a bit. I checked everything he wrote over and over again, and it seems to be working for everyone exept me :C Could anyone please help me?

This is the code for the Arm rotation

Graphic = The player/character

 using UnityEngine;
 using System.Collections;
 
 public class ArmRotation : MonoBehaviour {
 
     public int rotationOffset = 90;
 
     // Update is called once per frame
     void Update () {
         // subtracting the position of the player from the mouse position.
         Vector3 difference = Camera.main.ScreenToWorldPoint (Input.mousePosition) - transform.position;   
         difference.Normalize (); // normalizing the vector. Meaning that all the sum of the vector will be equal to 1.
 
         float rotZ = Mathf.Atan2 (difference.y, difference.x) * Mathf.Rad2Deg;  //find the angle in degrees
         transform.rotation = Quaternion.Euler (0f, 0f, rotZ + rotationOffset);
     }
 }
 

This is the code for the player movements (changed the script to make the arm not flip with the character)(only changed at the bottom and close to the top)

     [SerializeField] float maxSpeed = 10f;                // The fastest the player can travel in the x axis.
     [SerializeField] float jumpForce = 400f;            // Amount of force added when the player jumps.    
 
     [Range(0, 1)]
     [SerializeField] float crouchSpeed = .36f;            // Amount of maxSpeed applied to crouching movement. 1 = 100%
     
     [SerializeField] bool airControl = false;            // Whether or not a player can steer while jumping;
     [SerializeField] LayerMask whatIsGround;            // A mask determining what is ground to the character
     
     Transform groundCheck;                                // A position marking where to check if the player is grounded.
     float groundedRadius = .2f;                            // Radius of the overlap circle to determine if grounded
     bool grounded = false;                                // Whether or not the player is grounded.
     Transform ceilingCheck;                                // A position marking where to check for ceilings
     float ceilingRadius = .01f;                            // Radius of the overlap circle to determine if the player can stand up
     Animator anim;                                        // Reference to the player's animator component.
 
     Transform playerGraphics;                           // Reference to the Graphics so we can change direction
 
     void Awake()
     {
         // Setting up references.
         groundCheck = transform.Find("GroundCheck");
         ceilingCheck = transform.Find("CeilingCheck");
         anim = GetComponent<Animator>();
         playerGraphics = transform.FindChild ("Graphics");
         if (playerGraphics == null)
         {
             Debug.LogError ("Dont freak out! There is no 'Graphics' object as a child of the player");
         }
     }
 
 
     void FixedUpdate()
     {
         // The player is grounded if a circlecast to the groundcheck position hits anything designated as ground
         grounded = Physics2D.OverlapCircle(groundCheck.position, groundedRadius, whatIsGround);
         anim.SetBool("Ground", grounded);
 
         // Set the vertical animation
         anim.SetFloat("vSpeed", rigidbody2D.velocity.y);
     }
 
 
     public void Move(float move, bool crouch, bool jump)
     {
 
 
         // If crouching, check to see if the character can stand up
         if(!crouch && anim.GetBool("Crouch"))
         {
             // If the character has a ceiling preventing them from standing up, keep them crouching
             if( Physics2D.OverlapCircle(ceilingCheck.position, ceilingRadius, whatIsGround))
                 crouch = true;
         }
 
         // Set whether or not the character is crouching in the animator
         anim.SetBool("Crouch", crouch);
 
         //only control the player if grounded or airControl is turned on
         if(grounded || airControl)
         {
             // Reduce the speed if crouching by the crouchSpeed multiplier
             move = (crouch ? move * crouchSpeed : move);
 
             // The Speed animator parameter is set to the absolute value of the horizontal input.
             anim.SetFloat("Speed", Mathf.Abs(move));
 
             // Move the character
             rigidbody2D.velocity = new Vector2(move * maxSpeed, rigidbody2D.velocity.y);
             
             // If the input is moving the player right and the player is facing left...
             if(move > 0 && !facingRight)
                 // ... flip the player.
                 Flip();
             // Otherwise if the input is moving the player left and the player is facing right...
             else if(move < 0 && facingRight)
                 // ... flip the player.
                 Flip();
         }
 
         // If the player should jump...
         if (grounded && jump) {
             // Add a vertical force to the player.
             anim.SetBool("Ground", false);
             rigidbody2D.AddForce(new Vector2(0f, jumpForce));
         }
     }
 
     
     void Flip ()
     {
         // Switch the way the player is labelled as facing.
         facingRight = !facingRight;
         
         // Multiply the player's x local scale by -1.
         Vector3 theScale = playerGraphics.localScale;
         theScale.x *= -1;
         playerGraphics.localScale = theScale;
     }
 }