does not exist in the current context error

Is the AdvancedPlayer variable of the type Gameobject? If not and also if you don't declare the AdvancedPlayer variable anywhere you should do:

 Gameobject AdvancedPlayer = Gameobject.Find("A......

Also you should avoid gameobject.find in OnGUI and Update functions. You should assign the variable only once (for example in Start() or using the Component Inspector) because what you're trying to do there can cause massive performance-issues. Also the Component-Array you are trying to assign there should be assigned only once.

$$anonymous$$ake sure that you really have a gameobject with the name AdvancedPlayer. Also I would recommend you to maybe use tags ins$$anonymous$$d of names to find a gameoject.

if this helps here is my current script:

 using UnityEngine;
 using System.Collections;
 
 public class Questing : $$anonymous$$onoBehaviour {
     
     private float x;
 
     private float y;
     
     private GameObject AdvancedPlayer;
 
     private Vector2 resolution;
     
     public int quest = 0;    
     
     // Use this for initialization
     void Start () {
         
         GameObject AdvancedPlayer = GameObject.Find("AdvancedPlayer");
         
         resolution = new Vector2(Screen.width, Screen.height);
 
         x=Screen.width/1920.0f; // 1920 is the x value of the working resolution (as described in the first point)
 
         y=Screen.height/1080.0f; // 1042 is the y value of the working resolution (as described in the first point)
     }
     
     // Update is called once per frame
     void Update () {
         
         if(Screen.width!=resolution.x || Screen.height!=resolution.y)
            {
                resolution=new Vector2(Screen.width, Screen.height);
                x=resolution.x/1920.0f;
                y=resolution.y/1080.0f;
            }
     }        
     
     void OnGUI () {
         vp_FPPlayerEventHandler Player = AdvancedPlayer.transform.root.GetComponentInChildren<vp_FPPlayerEventHandler>();
         if(quest == 1){
             
         GUI.Box(new Rect(500*x,20*y,100*x,50*y), "Quests");
         GUI.Button(new Rect(500*x,40*y,100*x,50*y), "Here! take this mace to start questing! - Reward = $$anonymous$$ace");
         Player.SetWeapon.TryStart(1);    
     }    
     }
     
 void OnTriggerEnter (Collider other) {
 quest = 1;        
 }
 void OnTriggerExit (Collider other) {
 quest = 0;        
 }    
     
     
 }
 

What is not working correctoly? are you getting any errors? Please give us more detail about your issue.