How do i run a function from within another script?

Hello, i think i've solved the issue i ahd yesterday with accessing another script, i did remake one of them so that they both are made in c#. Now i have another issue.

What i want it to do is that when the box (enemyscripts "owner") is close enough to the player. I want it to run a damage function from within "healthbarscript". But i gett a null reference what not shit whenever he hits my player. I have no idea of why this is as it is.

Could somehere here spot the issue?

Healthbarscript:

 using UnityEngine;
 using System.Collections;
 
 
 public class HealthBarScript : MonoBehaviour {
     //varablar. Namnen talar för sig själva
     public int Maximumhealth = 100;
     public int CurrentHealth = 100;
     
     public float healthBarLength;
     
     // Use this for initialization
     void Start () {
         healthBarLength = Screen.width / 2;
     }
     
     // Update is called once per frame
     void Update () {
         AdjustCurrentHealth(0);
     }
     //Skapar healthboxen
     void OnGUI(){
         GUI.Box(new Rect(10, 10, healthBarLength, 20),
                 CurrentHealth + "/" + Maximumhealth);    
     }
     //Förhindrar division med 0 etc.
     public void AdjustCurrentHealth(int adj){
         CurrentHealth += adj;
         
         if(CurrentHealth < 0){
             CurrentHealth = 0;    
         }
         
         if(CurrentHealth > 100)
         {
             CurrentHealth = Maximumhealth;    
         }
         
         if(Maximumhealth < 1){
             Maximumhealth = 1;    
         }
         
         healthBarLength = (Screen.width / 2) * (CurrentHealth / (float)Maximumhealth);
     }
     //förlora hp functionen
     public void DamageFunction(int Damage)
     {
         CurrentHealth -= Damage;    
     }
 }
 
 
 
 Enemyscript:
 
 
 using UnityEngine;
 using System.Collections;
 
 public class EnemyMovement2 : MonoBehaviour {
     
     //Variabler
     public Transform target;
     new int moveSpeed = 3;
     new int rotationSpeed = 3;
     
     private Transform myTransform;
     
     void Awake(){
         //Gör så att man har sin egna transform redo
         myTransform = transform;    
     }
     
     // Use this for initialization
     void Start () {
         
     }
     
     // Update is called once per frame
     void Update () {
         
         //Sätter varablen target till ett GameObject
         GameObject go = GameObject.FindGameObjectWithTag("Player");
         
         target = go.transform;
         //rotationen
         myTransform.rotation = Quaternion.Slerp(myTransform.rotation, Quaternion.LookRotation(target.position - myTransform.position), rotationSpeed * Time.deltaTime);
         //rörelsen emot spelaren
         myTransform.position += myTransform.forward * moveSpeed * Time.deltaTime;
         //En debug linje för att se tydligare rörelser
         Debug.DrawLine(target.transform.position, myTransform.position);
         
         
         //Mäter avståndet emellan kuben och Playern
         float distance = Mathf.Sqrt( Mathf.Pow(target.position.x-myTransform.position.x,2) + Mathf.Pow(target.position.z-myTransform.position.z,2) );
         //Debug.Log(distance);
         
         //Mäter om den är tillräckligt nära för att "slå" dig
         if(distance < 1){
             Debug.Log("Fuck you, coptard");
             // Kör DamageFunction i "HealthBarScript"
             HealthBarScript healthbarscript = GetComponent<HealthBarScript>();
             healthbarscript.DamageFunction(5);
             
         }
     }
 
 }

Thanks in advance! :)