Car Select/Shop Bug

Hello! I have a bug in the car select/shop: The bug is, after I buy the car, I press either left or right, but when I go back to the car I bought, it says Buy again. Here are some of my scripts:

Coins Script

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.UI;
 
 public class Coins : MonoBehaviour
 {
     public Text coinsText;
     public GameObject buyBtn;
     public GameObject okBtn;
     public GameObject noCoinsScreen;
     static Dictionary<string, int> carPrices = new Dictionary<string, int>();
     // Start is called before the first frame update
     void Start()
     {
         //PlayerPrefs.DeleteAll();
         if(PlayerPrefs.HasKey("coins")==false)
         PlayerPrefs.SetInt("coins", 100);
 
         if(PlayerPrefs.HasKey("car2Lock")==false)
         {
             PlayerPrefs.SetString("car2Lock", "true");
         }
         if (PlayerPrefs.HasKey("car3Lock") == false)
         {
             PlayerPrefs.SetString("car3Lock", "true");
         }
 
         coinsText.text = "Coins" + ":" + " " + PlayerPrefs.GetInt("coins");
         if (carPrices.ContainsKey("Car2") == false)
             carPrices.Add("Car2", 100);
         if (carPrices.ContainsKey("Car3") == false)
             carPrices.Add("Car3", 200);
 
 
     }
 
     public void BuyCar()
     {
         int currentcoins = PlayerPrefs.GetInt("coins");
         if(currentcoins>=carPrices[Options.getCar()])
         {
             currentcoins = currentcoins - carPrices[Options.getCar()];
             PlayerPrefs.SetInt("coins", currentcoins);
 
             coinsText.text = "Coins" + ":" + " " + PlayerPrefs.GetInt("coins");
 
             PlayerPrefs.SetString(Options.getCar()+"Lock", "false");
             buyBtn.SetActive(false);
             okBtn.SetActive(true);
         }
 
         else
         {
             StartCoroutine(showNoCoins());
         }
     }
     IEnumerator showNoCoins()
     {
         noCoinsScreen.SetActive(true);
         yield return new WaitForSeconds(1);
         noCoinsScreen.SetActive(false);
 
     }
 
     // Update is called once per frame
     void Update()
     {
         
     }
 }

Select Car Script

 using System.Collections;
 using System.Collections.Generic;
 using UnityEngine;
 
 public class SelectCar : MonoBehaviour
 {
     public GameObject[] cars;
 
     static int index = 1;
     public GameObject okBtn;
     public GameObject buyBtn;
 
     // Start is called before the first frame update
     void Start()
     {
         
 
     }
 
     public static void resetIndex()
     {
         index = 1;
     }
 
     public void nextCar()
     {
         index = index + 1;
         if(index == 2)
         {
             foreach(GameObject car in cars)
             {
                 car.SetActive(false);
             }
             cars[1].SetActive(true);
             Options.setCar("Car2");
             if(PlayerPrefs.GetString("car2Lock")=="false")
             {
                 okBtn.SetActive(true);
                 buyBtn.SetActive(false);
             }
             else
             {
                 okBtn.SetActive(false);
                 buyBtn.SetActive(true);
             }
 
         }
 
         else if (index == 3)
         {
             foreach (GameObject car in cars)
             {
                 car.SetActive(false);
             }
             cars[2].SetActive(true);
             Options.setCar("Car3");
             if (PlayerPrefs.GetString("car3Lock") == "false")
             {
                 okBtn.SetActive(true);
                 buyBtn.SetActive(false);
             }
             else
             {
                 okBtn.SetActive(false);
                 buyBtn.SetActive(true);
             }
 
         }
         else
         {
             index = 3;
         }
     }
     
     public void previousCar()
     {
         index = index - 1;
 
         if(index==1)
         {
             foreach (GameObject car in cars)
             {
                 car.SetActive(false);
             }
             cars[0].SetActive(true);
             Options.setCar("Car1");
             okBtn.SetActive(true);
             buyBtn.SetActive(false);
         }
 
         else if (index == 2)
         {
             foreach (GameObject car in cars)
             {
                 car.SetActive(false);
             }
             cars[1].SetActive(true);
             Options.setCar("Car2");
             if (PlayerPrefs.GetString("car2Lock") == "false")
             {
                 okBtn.SetActive(true);
                 buyBtn.SetActive(false);
             }
             else
             {
                 okBtn.SetActive(false);
                 buyBtn.SetActive(true);
             }
 
         }
 
         
 
         else
         {
             index = 1;
         }
 
 
 
 
 
 
     }
 
 
 }