Following the mouse Cursor does not work correctly after Flip() Function

Hi, I am working on a simple 2D Game right now. I use a function called flip() to let the charakter always look to the side I am walking to. He carries a weapon and the weapon should always point in direction of the mouse pointer. When I'm walking to the right, it works but when I walk to the left and the Flip function kicks in, the Weapon is moving exactly to the opposite site of the mouse pointer. I tried to change something with the calculation which determines the angle, but I couldnt figure it out correctly... I added the code below. I hope someone can help me!

 PLAYER CODE:
 
 using UnityEngine;
 
 namespace UnitySampleAssets._2D
 {
 
     public class PlatformerCharacter2D : MonoBehaviour
     {
         private bool facingRight = true; // For determining which way the player is currently facing.
 
         [SerializeField] private float maxSpeed = 10f; // The fastest the player can travel in the x axis.
         [SerializeField] private float jumpForce = 400f; // Amount of force added when the player jumps.    
 
         [Range(0, 1)] [SerializeField] private float crouchSpeed = .36f;
                                                      // Amount of maxSpeed applied to crouching movement. 1 = 100%
 
         [SerializeField] private bool airControl = false; // Whether or not a player can steer while jumping;
         [SerializeField] private LayerMask whatIsGround; // A mask determining what is ground to the character
 
         private Transform groundCheck; // A position marking where to check if the player is grounded.
         private float groundedRadius = .2f; // Radius of the overlap circle to determine if grounded
         private bool grounded = false; // Whether or not the player is grounded.
         private Transform ceilingCheck; // A position marking where to check for ceilings
         private float ceilingRadius = .01f; // Radius of the overlap circle to determine if the player can stand up
         private Animator anim; // Reference to the player's animator component.
 
         Transform playerGraphics; //reference to graphics
 
         private void Awake()
         {
             // Setting up references.
             groundCheck = transform.Find("GroundCheck");
             ceilingCheck = transform.Find("CeilingCheck");
             anim = GetComponent<Animator>();
             //playerGraphics=transform.FindChild("Graphics");
             playerGraphics=transform.FindChild("Graphics");
             if(playerGraphics==null){
                 Debug.Log("fehler mit grafik, platformchar 2d");
             }
         }
 
 
         private 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", GetComponent<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
                 GetComponent<Rigidbody2D>().velocity = new Vector2(move*maxSpeed, GetComponent<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 && anim.GetBool("Ground"))
             {
                 // Add a vertical force to the player.
                 grounded = false;
                 anim.SetBool("Ground", false);
                 GetComponent<Rigidbody2D>().AddForce(new Vector2(0f, jumpForce));
             }
         }
 
 
         private 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;
         }
     }
 }
 
 
 ARM ROTATION CODE:
 
 using UnityEngine;
 using System.Collections;
 
 public class ArmRotation : MonoBehaviour {
 
     public int rotationOffset;
 
     // 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);
         
     }
 }