How to make a game object from several game objects in Unity?

Dear Unity fourm I have programmed a great music game. Unfortunately there is a problem. In my game there are so many objects that my smartphone can't load the game properly. I have nowhere to find out how to make an object out of many objects. If someone knows how to do it I would be very happy!

My Script:

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

public class line : MonoBehaviour {

 //Please attach me to the line, then set  dline,tail,mcamera,road,decorates,dieeff.
 //You can add more to make this better!
 public GameObject dline, tail, mcamera, road, decorates, dieeff;

 private GameObject tempgo, tempdia, tempcr;

 public bool direction, alive, start, load, roadmaker;

 public float cameraspeed, temprm;

 public Vector3 offset, tempcrgo;

 private GameObject[] dia, cr;

 List<GameObject> go = new List<GameObject>();

 void Start()
 {
     start = false;
     load = true;
     alive = true;
     //find diamonds and crowns
     dia = GameObject.FindGameObjectsWithTag("dia");
     cr = GameObject.FindGameObjectsWithTag("crown");
     //
 }

 void Update()
 {
     if (load == true)
     {
         //save the initial distance between camera and line
         offset = mcamera.transform.position - dline.transform.position;
         cameraspeed = 0.03f;
         load = false;
         //
     }
     //restart
     if (Input.GetKeyDown(KeyCode.R) == true)
     {
         SceneManager.LoadScene("main");
     }
     //
     if (start == false && alive == true)
     {//start game
         if (Input.GetMouseButtonDown(0) == true || Input.GetKeyDown(KeyCode.Space) == true)
         {
             start = true;
             dline.GetComponent<AudioSource>().enabled = true;
         }

     }//

     if (start == true)
     {//turn
         if (Input.GetMouseButtonDown(0) == true || Input.GetKeyDown(KeyCode.Space) == true)
         {
             if (direction == true)
             {
                 direction = false;
             }
             else
             {
                 direction = true;
             }
         }
     }//
      //build road/wall more efficiently
     if (roadmaker)
     {
         temprm += 1;
         //why there is temprm?to reduce the ammount of roads
         //why build one when click?to ensure there is road/wall when line turns(or it will look weird)
         if (temprm % 6 == 1 || Input.GetMouseButtonDown(0) == true || Input.GetKeyDown(KeyCode.Space) == true)
         {
             GameObject.Instantiate(road, dline.transform.position + new Vector3(3, 0, -3), dline.transform.rotation);
             GameObject.Instantiate(road, dline.transform.position + new Vector3(-3, 0, 3), dline.transform.rotation);
         }// // //
     }
     else
     {//when you play ...I dont put the part in Update but if(roadmaker) because these actions will create new gameobject and interfere the copying of road
         GameObject.Instantiate(tail, dline.transform.position, dline.transform.rotation);
         if (Input.GetMouseButtonDown(0) == true || Input.GetKeyDown(KeyCode.Space) == true)
         {
             if (direction == true)
             {
                 go.Add(GameObject.Instantiate(decorates, dline.transform.position + new Vector3(8, -9, -5), dline.transform.rotation));
             }
             else
             {
                 go.Add(GameObject.Instantiate(decorates, dline.transform.position + new Vector3(-5, -9, 8), dline.transform.rotation));
             }
         }
     }//
 }

 void FixedUpdate()
 {//smooth camera
     mcamera.transform.position = Vector3.Lerp(mcamera.transform.position, offset + dline.transform.position, cameraspeed);
     //
     //some 'animations' .I didnt use animation component because I dont know how it works in Unity :(
     foreach (GameObject tempgo in go)
     {
         tempgo.transform.position += new Vector3(0, 0.2f, 0);
     }

     foreach (GameObject tempdia in dia)
     {
         tempdia.transform.localEulerAngles += new Vector3(0, 2, 0);
         if (Mathf.Abs(dline.transform.position.x - tempdia.transform.position.x) < 1 && Mathf.Abs(dline.transform.position.z - tempdia.transform.position.z) < 1 && tempdia.transform.localScale.z > 0)
         {
             tempdia.transform.localScale -= new Vector3(0.3f, 0.3f, 0.3f);
         }
     }
     foreach (GameObject tempcr in cr)
     {
         tempcr.transform.localEulerAngles += new Vector3(0, 2, 0);
         if (Mathf.Abs(dline.transform.position.x - tempcr.transform.position.x) < 2 && Mathf.Abs(dline.transform.position.z - tempcr.transform.position.z) < 2 && tempcr.transform.localScale.z > 0)
         {
             tempcr.transform.localScale -= new Vector3(0.26f, 0.26f, 0.26f);
             tempcrgo = tempcr.transform.position;
         }
         if (tempcr.transform.localScale.z <= 0)
         {
             tempcrgo += new Vector3(Random.Range(-2f, 2f), Random.Range(-1f, 2f), Random.Range(-2f, 2f));
             tempcr.GetComponent<Light>().enabled = true;
             tempcr.transform.position = Vector3.Lerp(tempcr.transform.position, tempcrgo, 0.02f);

         }
     }
     //
     if (start == true && alive == true)
     {//how the line move
         if (direction == true)
         {
             dline.transform.position += new Vector3(0.3f, 0, 0);
         }
         else
         {
             dline.transform.position += new Vector3(0, 0, 0.3f);
         }
     }//
 }

 void OnCollisionEnter(Collision x)
 {//when die...
     if (x.collider.tag == "wall")
     {
         alive = false;
         mcamera.GetComponent<AudioSource>().enabled = true;
         dieeff.SetActive(true);
     }// 
      //when complete the level...
     if (x.collider.tag == "Finish")
     {
         offset = offset + offset + offset + offset;
         cameraspeed = 0.01f;
     }//
 }

}

`

Video Link:

https://drive.google.com/file/d/1dqIqu6tx5thNbCJ1jNndXEJY_a9JJGGe/view?usp=sharing