Scene doesn't reload properly

Hello!

My project is cloning tetris. I added a MainMenu and a GameOver scene. In the GameOver scene I made a "respawn" button which uses SceneManager to re-load the MainGameScene. But after loading it from the GameOver scene, the speed is the same it was when the MainGameScene ended (very fast) instead of being how it was when firstly loading the MainGameScene (slow). Can anyone help me? I think it's because of increasing speed after a certain amount of time, which doesn't reset when I reload the scene. But since I'm a beginner, I'm not sure how to fix it.. Here is my code:

  using System.Collections;
  using System.Collections.Generic;
  using UnityEngine;
  using UnityEngine.UI;
  using UnityEngine.SceneManagement;
  
  public class Shape : MonoBehaviour
  {
      public static float speed = 1.0f;
  
      float lastMoveDown = 0;
  
      void Start()
      {
          if(!IsInGrid())
          {
              SoundManager.Instance.PlayOneShot(SoundManager.Instance.gameOver);
  
              Invoke("OpenGameOverScene", .5f);
          }
  
          InvokeRepeating("IncreaseSpeed", 2.0f, 2.0f);
      }
  
      void OpenGameOverScene()
      {
          Destroy(gameObject);
          SceneManager.LoadScene("GameOver");
      }
  
      void IncreaseSpeed()
      {
          Shape.speed -= .001f;
      }
  
      // Update is called once per frame
      void Update()
      {
          if(Input.GetKeyDown("a"))
          {
              transform.position += new Vector3(-1, 0, 0);
  
              if(!IsInGrid())
              {
                  transform.position += new Vector3(1, 0, 0);
              }
              else
              {
                  UpdateGameBoard();
                  SoundManager.Instance.PlayOneShot(SoundManager.Instance.shapeMove);
              }
          }
  
          if (Input.GetKeyDown("d"))
          {
              transform.position += new Vector3(1, 0, 0);
  
              if (!IsInGrid())
              {
                  transform.position += new Vector3(-1, 0, 0);
              }
              else
              {
                  UpdateGameBoard();
                  SoundManager.Instance.PlayOneShot(SoundManager.Instance.shapeMove);
              }
          }
  
          if (Input.GetKeyDown("s") || Time.time - lastMoveDown >= Shape.speed)
          {
              transform.position += new Vector3(0, -1, 0);
  
              if (!IsInGrid())
              {
                  transform.position += new Vector3(0, 1, 0);
  
                  bool rowDeleted = GameBoard.DeleteAllFullRows();
  
                  if(rowDeleted)
                  {
                      GameBoard.DeleteAllFullRows();
                  }
  
                  enabled = false;
  
                  FindObjectOfType<ShapeSpawner>().SpawnShape();
  
                  SoundManager.Instance.PlayOneShot(SoundManager.Instance.shapeStop);
              }
              else
              {
                  UpdateGameBoard();
                  SoundManager.Instance.PlayOneShot(SoundManager.Instance.shapeMove);
              }
              lastMoveDown = Time.time;
  
          }
  
          if (Input.GetKeyDown("w"))
          {
              transform.Rotate(0, 0, 90);
  
              if (!IsInGrid())
              {
                  transform.Rotate(0, 0, -90);
              }
              else
              {
                  UpdateGameBoard();
                  SoundManager.Instance.PlayOneShot(SoundManager.Instance.rotateSound);
              }
  
          }
  
          if (Input.GetKeyDown("e"))
          {
              transform.Rotate(0, 0, -90);
  
              if (!IsInGrid())
              {
                  transform.Rotate(0, 0, 90);
              }
              else
              {
                  UpdateGameBoard();
                  SoundManager.Instance.PlayOneShot(SoundManager.Instance.rotateSound);
              }
  
          }
      }
  
      public bool IsInGrid()
      {
  
          foreach (Transform childBlock in transform)
          {
              Vector2 vect = RoundVector(childBlock.position);
  
              if(!IsInBorder(vect))
              {
                  return false;
              }
  
              if(GameBoard.gameBoard[(int)vect.x, (int)vect.y] != null && GameBoard.gameBoard[(int)vect.x, (int)vect.y].parent != transform)
              {
                  return false;
              }
          }
  
          return true;
      }
  
      public Vector2 RoundVector(Vector2 vect)
      {
          return new Vector2(Mathf.Round(vect.x), Mathf.Round(vect.y));
      }
  
      public static bool IsInBorder(Vector2 pos )
      {
          return ((int)pos.x >= 0 && (int)pos.x <= 9 && (int)pos.y >= 0);
      }
  
      public void UpdateGameBoard()
      {
          for(int y = 0; y<20; ++y)
          {
              for(int x = 0; x<10; ++x)
              {
                  if(GameBoard.gameBoard[x,y] != null && GameBoard.gameBoard[x, y].parent == transform)
                  {
                      GameBoard.gameBoard[x, y] = null;
                  }
              }
          }
  
          foreach(Transform childBlock in transform)
          {
              Vector2 vect = RoundVector(childBlock.position);
              GameBoard.gameBoard[(int)vect.x, (int)vect.y] = childBlock;
  
              //Debug.Log("Cube at" + vect.x + " " + vect.y);
          }
      }
  
  }