4 errors in 1 script. Unexpected symbols and more, help please?

I know it's a long script, but please can somebody help me? I'm struggling with these problems for over three weeks :( And I don't know how to solve it... Please :)

 using System.Collections;
 using UnityEngine;
 
 //List of all the posible gamestates
 public enum GameState
 {
     NotStarted,
     Playing,
     Completed,
     Failed
 }
 
 //Make sure there is always an AudioSource component on the GameObject where this script is added.
 [RequireComponent(typeof(AudioSource))]
 public class GameManager : MonoBehaviour
 {
     //Text element to display certain messages on
     public GUIText FeedbackText;
     
     //Text to be displayed when entering one of the gamestates
     public string GameNotStartedText;
     public string GameCompletedText;
     public string GameFailedText;
     
     //Sounds to be played when entering one of the gamestates
     public AudioClip StartSound;
     public AudioClip FailedSound;
     
     private GameState currentState = GameState.NotStarted;
     //All the blocks found in this level, to keep track of how many are left
     private Block[] allBlocks;
     private Ball[] allBalls;
     
     // Use this for initialization
     void Start()
     {
         //Find all the blocks in this scene
         allBlocks = FindObjectsOfType(typeof(Block)) as Block[];
         
         //Find all the balls in this scene
         allBalls = FindObjectsOfType(typeof(Ball)) as Ball[];
         
         //Prepare the start of the level
         SwitchTo(GameState.NotStarted);
     }
     
     // Update is called once per frame
     void Update()
     {
         switch (currentState)
         {
         case GameState.NotStarted:
             //Check if the player taps/clicks.
             if (Input.GetMouseButtonDown(0))    //Note: on mobile this will translate to the first touch/finger so perfectly multiplatform!
             {
                 for (int i = 0; i < allBalls.Length; i++)
                     allBalls[i].Launch();
                 
                 SwitchTo(GameState.Playing);
             }
             break;
         case GameState.Playing:
         {
             bool allBlocksDestroyed = true;
             
             //Check if all blocks have been destroyed
             for (int i = 0; i < allBlocks.Length; i++)
             {
                 if (!allBlocks[i].BlockIsDestroyed)
                 {
                     allBlocksDestroyed = false;
                     break;
                 }
             }
             
             //Are there no balls left?
             if (FindObjectOfType(typeof(Ball)) == null)
                 SwitchTo(GameState.Failed);
             
             if (allBlocksDestroyed)
                 SwitchTo(GameState.Completed);
 
             switch (currentState)
             
             
                 if(GameState.Failed){
                 Application.LoadLevel("Menu")}
                 if(GameState.Completed){
                 Application.LoadLevel("Level 2")}
                 
                         
                         //Check if the player taps/clicks.
                         if (Input.GetMouseButtonDown(0))    //Note: on mobile this will translate to the first touch/finger so perfectly multiplatform!
                             Restart()
                                 break;
                 }
         }
             
             //Do the appropriate actions when changing the gamestate
             public void SwitchTo(GameState newState){
             }
     
                 currentState = newState;
                 
             switch (currentState){
 
             default:
             case GameState.NotStarted:
             DisplayText(GameNotStartedText);
             break;
             case GameState.Playing:
             audio.PlayOneShot(StartSound);
             DisplayText("");
             break;
             case GameState.Completed:
             audio.PlayOneShot(StartSound);
             DisplayText(GameCompletedText);
             StartCoroutine(RestartAfter(StartSound.length));
             break;
             case GameState.Failed:
             audio.PlayOneShot(FailedSound);
             DisplayText(GameFailedText);
             StartCoroutine(RestartAfter(FailedSound.length));
             break;
         }
             
             //Helper to display some text
             private void DisplayText(string text){
             }
         {
             FeedbackText.text = text;
         }
             
             //Coroutine which waits and then restarts the level
             //Note: You need to call this method with StartRoutine(RestartAfter(seconds)) else it won't restart
             private IEnumerator RestartAfter(float seconds){
                 {
                     yield return new WaitForSeconds(seconds);
                     
                     Restart();
                 }
                 
                 //Helper to restart the level
                 private void Restart()
                 {
                     Application.LoadLevel(0);
                 }
             }