Difficulty Options Not working

Okay so Im new to code and I made this script to change the speed and spawn rate when you click the button difficulty but this appears and nothings changes when I click the button:
NullReferenceException: Object reference not set to an instance of an object
Difficulty.Medium () (at Assets/Difficulty.cs:26)

The code I have in the script is this one

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

public class Difficulty : MonoBehaviour
{

public PipeMoveScript movespeed;
public PipeSpawnScript spawner;

void Start() //In here I access the variables from different scripts
{
movespeed = GameObject.FindGameObjectWithTag(“MoveSpeed”).GetComponent();
spawner = GameObject.FindGameObjectWithTag(“Spawner”).GetComponent();
}

public void Easy() // for example In here I try to change these variables and then apply the script in the button when clicked but nothing changes
{
movespeed.moveSpeed = 5;
spawner.spawnRate = 3;
Debug.Log(“Easy Difficulty”);
}

public void Medium()
{
movespeed.moveSpeed = 7;
spawner.spawnRate = 2;
Debug.Log(“Medium Difficulty”);
}

public void Hard()
{
movespeed.moveSpeed = 10;
spawner.spawnRate = 1;
Debug.Log(“Hard Difficulty”);

}
}

Use code tags when posting code.

Solving a null ref error is always the same

  1. Find out what is null
  2. Find out why it’s null
  3. Fix it.

Either movespeed or spawner is null. Go to line 26 and you’ll know which. Then find out why it doesn’t have a value.