Creating a Quest system

Okay Well I now am making a quest / dialogue system and I'm stuck on finishing the quest exp "go talk to your father" "STUCK PART"

I'm using C#

 using UnityEngine;
 using System.Collections;
 
 public class Speek : MonoBehaviour {
 
 // Use this for initialization
 
     
 public void Start ()
 {
 CurrentMenu = MainMenu;
 DisplayMenu = false;
 }
 
 // Update is called once per frame
 public void Update()
 {
 if (Input.GetMouseButtonDown(1))
 DisplayMenu = !DisplayMenu;
 }
 
 public void OnGUI()
 {
 if (DisplayMenu)
             
 CurrentMenu();
         
 }
 
 private delegate void MenuDelegate();
 
 private MenuDelegate CurrentMenu;
 private bool DisplayMenu;
 
     
     public string name;
     public string QuestPage1;
     public string QuestPage2;
     private bool Quest = false;
     public GameObject target;
 
 
 //
 // Main menu
 //
 private void MainMenu ()
 {
 Rect MainMenuRect = new Rect((Screen.width - 280) / 2, (Screen.height - 100) / 1.03f, 630, 108);
 GUI.BeginGroup(MainMenuRect);
 GUI.Box(new Rect(10, 10, MainMenuRect.width, MainMenuRect.height),  name );
         GUI.Label(new Rect(25, 25, 540, 80), QuestPage1 ); 
 
     
 
 if (GUI.Button(new Rect(540, 80, 80, 20), "Next"))
 {
 
 CurrentMenu = Next;
 }
     }   
         
         
         
 private void Next(){
 
 
 Rect OptionsRect = new Rect((Screen.width - 280) / 2, (Screen.height - 100) / 1.03f, 630, 108);
 GUI.BeginGroup(OptionsRect);
 GUI.Box(new Rect(10,10,OptionsRect.width,OptionsRect.height), name );
         GUI.Label(new Rect(25, 25, 540, 80), QuestPage2 );
         
 
 if (GUI.Button(new Rect(15, 80, 80, 20), "Back"))
 {
 
 CurrentMenu = MainMenu;
 }
 
 
 if (GUI.Button(new Rect(540, 80, 80, 20), "Okay"))
 {
 
 DisplayMenu = false;
 Quest = true;
                         
 }
     }    
         private void Quest () {
          if (Input.GetKeyDown("a")) {
     QuestPart1 = ;}
 
         }
         
 }