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;
	}
}

Same problem