Destory button on click and other problem

I'm trying to make a text adventure game and it starts off with a normal button to start the adventure, but I want the button to go away as soon as I click it so it's just text showing. I've used the Destroy method but it doesn't do anything. Here is my code:

 using UnityEngine;
 using UnityEngine.UI;
 using System.Collections;
 
 public class AnimatedDialog : MonoBehaviour
 {
     public string [] dialog;
     public float speed = 0.1f;
 
     private Text textArea;
     private bool isSpawned;
     private Button startButton;
 
     int stringIndex = 0;
     int characterIndex = 0;
 
     private void Start ()
     {
         StartCoroutine (DisplayTimer ());
         textArea = GameObject.Find ("Text").GetComponent<Text> ();
         startButton = Button.FindObjectOfType<Button> ();
     }
 
     public void OnClick ()
     {
         if (!isSpawned)
         {
             Instantiate (this, new Vector3 (0f, 0f), Quaternion.identity);
             
             isSpawned = true;
         }
         else
         {
             Destroy (startButton);
             return;
         }
     }
 
     IEnumerator DisplayTimer ()
     {
         while (1 == 1)
         {
             yield return new WaitForSeconds (speed);
             if (characterIndex > dialog [stringIndex].Length)
             {
                 continue;
             }
 
             textArea.text = dialog [stringIndex].Substring (0, characterIndex);
             characterIndex++;
         }
     }
 
     private void Update ()
     {
         if (Input.GetButtonDown("Jump"))
         {
             if(characterIndex < dialog [stringIndex].Length)
             {
                 characterIndex = dialog [stringIndex].Length;
             }
             else if(stringIndex < dialog.Length)
             {
                 stringIndex++;
                 characterIndex = 0;
             }
         }
     }
 }
 

The other problem I'm having is when I press space to make the text go, it makes another instance of the dialog prefab even though I'm not clicking the button anymore, why is this happening? I've tried making a separate script to just destroy the button but it's still there? Is there something I'm missing about the destroy method?