Problems with unlocking levels

In the menu I put an option for the levels to be unlocked as I pass them. In this case, once passed, I can choose the level that I already passed. At the moment I have 10 levels. To give an example, it happens to me that when I choose to start from level 5 and go to level 6, the following are blocked. From 7 to 10 they are blocked and I have to unblock them again. How could I modify the code so that once it is unlocked it does not lock again? Here is the script i'm using:

  using System.Collections;
  using System.Collections.Generic;
  using UnityEngine;
  using UnityEngine.UI;
  using UnityEngine.SceneManagement;
   
  public class LevelSelector : MonoBehaviour
  {  
      public Button[] levelBTN;  
      public SceneLogic sceneLogic;
   
      void Start()
      {    
          //To unlock levels
          int level = PlayerPrefs.GetInt("level", 1);
   
          for (int i = 0; i < levelBTN.Length; i++)
          {
              if (i + 1 > level)
                  levelBTN[i].interactable = false;        
          }
      }
 
      public void levelToLoad(int level)
      {
          SceneManager.LoadScene(level);
       
      }      
   
      public void ButtonPressed1()
      {    
          sceneLogic.IndiceDeNiveles = 0;
          PlayerPrefs.SetInt("CorrespondingLevel", sceneLogic.LevelsIndex);
      }  
      public void ButtonPressed2()
      {    
          sceneLogic.IndiceDeNiveles = 1;
          PlayerPrefs.SetInt("CorrespondingLevel", sceneLogic.LevelsIndex);
      }  
      public void ButtonPressed3()
      {
          sceneLogic.IndiceDeNiveles = 2;
          PlayerPrefs.SetInt("CorrespondingLevel", sceneLogic.LevelsIndex);
      }  
      public void ButtonPressed4()
      {
          sceneLogic.IndiceDeNiveles = 3;
          PlayerPrefs.SetInt("CorrespondingLevel", sceneLogic.LevelsIndex);
      }  
      public void ButtonPressed5()
      {
          sceneLogic.IndiceDeNiveles = 4;
          PlayerPrefs.SetInt("CorrespondingLevel", sceneLogic.LevelsIndex);
      }  
      public void ButtonPressed6()
      {
          sceneLogic.IndiceDeNiveles = 5;
          PlayerPrefs.SetInt("CorrespondingLevel", sceneLogic.LevelsIndex);
      }  
      public void ButtonPressed7()
      {
          sceneLogic.IndiceDeNiveles = 6;
          PlayerPrefs.SetInt("CorrespondingLevel", sceneLogic.LevelsIndex);
      }  
      public void ButtonPressed8()
      {
          sceneLogic.IndiceDeNiveles = 7;
          PlayerPrefs.SetInt("CorrespondingLevel", sceneLogic.LevelsIndex);
      }  
      public void ButtonPressed9()
      {
          sceneLogic.IndiceDeNiveles = 8;
          PlayerPrefs.SetInt("CorrespondingLevel", sceneLogic.LevelsIndex);
      }  
      public void ButtonPressed10()
      {
          sceneLogic.IndiceDeNiveles = 9;
          PlayerPrefs.SetInt("CorrespondingLevel", sceneLogic.LevelsIndex);
      } 
  }

I should create a function that if it is 10 levels and I choose level 5, it should check if levels 6 to 10 are locked or unlocked. If they are unlocked, I should leave them unlocked if I go to 6. And if they are locked, I should leave them locked. Any idea how to do that?