game state (start and stop the game) i have bin sitting with this for a long time plzz help

private bool gameStarted = false;
[SerializeField]
private Text gameStateText;
[SerializeField]
private GameObject player;
[SerializeField]
private BirdMovement birdMovement;
[SerializeField]
private FollowCamera followCamera;
private float restartDelay = 3f;
private float restartTimer;
private playerMove playerMovement;
private PlayerHealth playerHealth;

// Use this for initialization
void Start () {
    Cursor.visible = false;

    playerMovement = GetComponent<playerMove> ();
    playerHealth = GetComponent<PlayerHealth> ();

    // privent the player from moving at the start of the game 
    playerMovement.enabled = false;

    // prevent the bird from moving at the start of the game 
    birdMovement.enabled = false;

    // prevent the follow camera to moving to its start potition 
    followCamera.enabled = false;

}

// Update is called once per frame
void Update () {

    // if the game is not started and the player presses the space bar...
    if (gameStarted == false && Input.GetKeyUp(KeyCode.Space)) {

        //... start the Game... 
        StartGame();


    }

    // if the player is no longer alive 
    if (playerHealth.Alive == false) {


        // ...then end the game 
        EndGame();

        //... increment a timer to count up to the restart
        restartTimer = restartTimer + Time.deltaTime;

        //... and if it reaches the restart delay...
        if (restartTimer >= restartDelay) {

            //...then reload the curent loadet sceen
            SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex);

        }
    }
}
private void StartGame() {

    //set the game state
    gameStarted = false;

    //removing the start text
    gameStateText.color = Color.clear;

    //allow the player to move 
    playerMovement.enabled = true;

    //allow the bird to move
    birdMovement.enabled = true;

    //allow the camera to move 
    followCamera.enabled = true;
}

private void EndGame() {

    //set game state 
    gameStarted = false;

    //set the gametext to gameover
    gameStateText.color = Color.white;
    gameStateText.text = "Game Over!";

    // romove the player from the game
    player.SetActive (false);
}