When you click the same image twice it see it says a match. Any thoughts on how to fix that?

Hi there i am trying to fix this code.There is 2 cards that have the same sprite example * symbol if two are seleced its a match.But after i click on the same image its says ita a match.How to make after i click the first button i stay deactivated or locked? Here is the code.

public class GameControler : MonoBehaviour {

 [SerializeField]
 private Sprite bgimage;
 public Sprite[] puzzles;
 public List<Sprite> gamePuzzles = new List<Sprite>();
 public List<Button> btns = new List<Button>();

 public GameObject Winnerpanel;

 private bool firstGuess, secondsGuess;
 private int countGuesses;
 private int countCorrectGuesses;
 private int gameGuesses;

 private int firstGuessIndex, secondGuessIndex;

 private string firstGuessPuzzle, secondGuessPuzzle;


 private void Awake()
 {
     //puzzles = Resources.LoadAll<Sprite>("Sprites/Candy");
 }


 // Use this for initialization
 void Start()
 {
     puzzles = Resources.LoadAll<Sprite>("Sprites/allgems");

     GetButtons();
     AddListeners();
     AddGamePuzzles();
     Shuffle(gamePuzzles);
     gameGuesses = gamePuzzles.Count / 2;
 }

 // Update is called once per frame
 void GetButtons()
 {
     GameObject[] objects = GameObject.FindGameObjectsWithTag("PuzzelButton");
     for (int i = 0; i < objects.Length; i++)
     {
         btns.Add(objects[i].GetComponent<Button>());
         btns[i].image.sprite = bgimage;
     }
 }

 void AddGamePuzzles()
 {
     int looper = btns.Count;
     int index = 0;

     for (int i = 0; i < looper; i++)
     {
         if (index == looper / 2)
             index = 0;
         {
             gamePuzzles.Add(puzzles[index]);
             index++;
         }
     }

 }

 void AddListeners()
 {
     foreach (Button btn in btns)
     {
         btn.onClick.AddListener(() => PickAtPuzzle());
     }
 }

 public void PickAtPuzzle()
 {
     string name = UnityEngine.EventSystems.EventSystem.current.currentSelectedGameObject.name;
     //Debug.Log("CLick" + name);

     if (!firstGuess)
     {
         firstGuess = true;

         firstGuessIndex = int.Parse(UnityEngine.EventSystems.EventSystem.current.currentSelectedGameObject.name);

         firstGuessPuzzle = gamePuzzles[firstGuessIndex].name;

         btns[firstGuessIndex].image.sprite = gamePuzzles[firstGuessIndex];
         Debug.Log("First" + name);
         


     }
     else if (!secondsGuess)
     {
         secondsGuess = true;
         secondGuessIndex = int.Parse(UnityEngine.EventSystems.EventSystem.current.currentSelectedGameObject.name);
         secondGuessPuzzle = gamePuzzles[secondGuessIndex].name;
         btns[secondGuessIndex].image.sprite = gamePuzzles[secondGuessIndex];

         countGuesses++;

         StartCoroutine(CheckIfThePuzzlesMatch());
         
     }

 }

 
 IEnumerator CheckIfThePuzzlesMatch()
 {

     yield return new WaitForSeconds(1f);
     
         if (firstGuessPuzzle == secondGuessPuzzle)
     {
         yield return new WaitForSeconds(.1f);
         btns[firstGuessIndex].interactable = false;
         btns[secondGuessIndex].interactable = false;

         btns[firstGuessIndex].image.color = new Color(0, 0, 0, 0);
         btns[secondGuessIndex].image.color = new Color(0, 0, 0, 0);

         CheckIfTheGameIsFinished();

     } else
     {
         yield return new WaitForSeconds(.1f);
         btns[firstGuessIndex].image.sprite = bgimage;
         btns[secondGuessIndex].image.sprite = bgimage;
     }

     yield return new WaitForSeconds (.1f);

     firstGuess = secondsGuess = false;

 }

 void CheckIfTheGameIsFinished()
 {
     countCorrectGuesses++;
     
     if (countCorrectGuesses == gameGuesses)
     {
         Winnerpanel.SetActive(true);

         Debug.Log("Game Finisshed");
         
         Debug.Log("It took you" + countGuesses + "many guess(es) to finish the game");
     }
 }

 void Shuffle(List<Sprite> list)
 {
     for(int i = 0; i < list.Count; i++)
     {
         Sprite temp = list[i];
         int randomIndex = Random.Range(0, list.Count);
         list[i] = list[randomIndex];
         list[randomIndex] = temp;
     }
 }

}