rotate position change?????

Hello I want to rotate object i use this

using System.Collections; using System.Collections.Generic; using UnityEngine;

public class KunaiArrow : MonoBehaviour {

 public Vector3 point;
 [SerializeField]
 Transform start;

 [SerializeField]
 Transform End;

 // Use this for initialization
 void Start () {
     Debug.Log(transform.position.y);


 }
 void Update()
 {

     Debug.Log(transform.position.y);
     input();
   
 }
 // Update is called once per frame
 void FixedUpdate () {
     checkstates();
 }

 

 private void checkstates()
 {
     if (Player.Instance.arrowrenge==true && this.gameObject.GetComponent<Renderer>().enabled == false)
     {
         Debug.Log("yes");
         this.gameObject.GetComponent<Renderer>().enabled = true;
     }
     if (Player.Instance.arrowrenge == false && this.gameObject.GetComponent<Renderer>().enabled == true)
     {
         Debug.Log("no");

         this.gameObject.GetComponent<Renderer>().enabled = false;
 
     }
 }

 private void input()
 {
     if (transform.position.y < start.position.y)
     {
         Debug.Log(transform.rotation.z);
         if (this.gameObject.GetComponent<Renderer>().enabled == true)
             if (Input.GetKey(KeyCode.W))
             {
                 transform.RotateAround(point, Vector3.forward, 20 * Time.deltaTime);
             }
     }
     if (transform.position.y > End.position.y)
     {
         Debug.Log(transform.position.y);
         if (Input.GetKey(KeyCode.S))
         {
             transform.RotateAround(point, -Vector3.forward, 20 * Time.deltaTime);
         }
     }
 }

}

it work put when i move the player the point change and that annoying i try several ways to make it work put no one work with me