Level script C# Unity

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEngine.SceneManagement;

public class Level : MonoBehaviour {

    float startTime;
    int numTreasures;
    int collected = 0;
    bool levelComplete = false;
    GameObject player;
    public float levelBottomY = -10f;
    GameObject kamera;


    // Use this for initialization
    void Start () {
        startTime = Time.time;
        GameObject[] treasureObjects = GameObject.FindGameObjectsWithTag("Treasure");
        numTreasures = treasureObjects.Length;
        player = GameObject.FindWithTag("Player");
        Cursor.visible = false;
        kamera = GameObject.FindWithTag("MainCamera");
}

	// Update is called once per frame
	void Update () {
		if (player!= null && player.transform.position.y < levelBottomY)
        {
            Kill();
        }
	}

    void Kill ()
    {
        kamera.transform.parent = null;
        GameObject.Destroy(player);
        levelComplete = true;
    }


    void TreasureCollected()
    {
        collected++;
        if (collected == numTreasures)
        {
            levelComplete = true;
    //        GameObject hiscores = GameObject.Find("Hiscores");
    //        if (hiscores != null)
    //        {
    //            hiscores.GetComponent<Hiscores>().StoreTime(SceneManager.GetActiveScene().buildIndex, Time.time - startTime);
    //        }
        }
    }

    bool LevelEndMessage(string message, string buttonText)
    {
        Cursor.visible = true;
        GUI.skin.label.alignment = TextAnchor.MiddleCenter;
        GUI.Label(new Rect(Screen.width / 2 - 200 / 2, Screen.height / 2 -75, 200, 50), message);
        return GUI.Button(new Rect(Screen.width / 2 - 200 / 2, Screen.height / 2 + 25, 200, 50), buttonText);
    }


    private void OnGUI()
    {
        GUI.skin.label.fontSize = 20;
        GUI.skin.label.alignment = TextAnchor.MiddleLeft;
        GUI.skin.label.alignment = TextAnchor.MiddleLeft;
        GUI.Label(new Rect(10, 10, 200, 30), "Time: " + (Time.time - startTime).ToString("#.##"));
        GUI.Label(new Rect(10, 40, 200, 30), "Treasures: " + collected + "/" + numTreasures);

        if (levelComplete)

        {
            if (player != null)
            {
                if (LevelEndMessage("Level completed!", "Continue"))
                {
                    int nextLevel = SceneManager.GetActiveScene().buildIndex + 1;
                    if (nextLevel >= SceneManager.sceneCountInBuildSettings)
                    { nextLevel = 0; }
                    SceneManager.LoadScene(nextLevel);
                }
            }

            else if (player == null)
            {
                if (LevelEndMessage("Level failed", "Retry"))
                {
                    SceneManager.LoadScene(SceneManager.GetActiveScene().buildIndex);
                }
                if (GUI.Button(new Rect(Screen.width / 2 - 200 / 2, Screen.height / 2 + 100, 200, 50)
                    , "Give up"))
                {
                    SceneManager.LoadScene(0);
                }
            }
        }
    }



}