How do I find if a string from list was used and exclude it from further use.

I am making a quiz game in Unity 2d and it's almost complete (excluding all the questions, but that's not important). All my questions and answers are in a List, they are in "questions" List and "correctAnswer" List. The questions are randomized and i want to make it that if a question is picked by random at least once, then it won't be used again, meaning it won't be used by the randomizer.

Sorry if i used something incorrectly, i'm a beginner. What is in questions is not important it's in another language. P.S. I am looking for how to make random range not to repeat.

  List<string> questions = new List<string>() { "Pasaules augstākais kalns?", "Kas ir Vācijas galvaspilsēta?", "Kur atrodas ASV?", "Geo jautājums 4", "jt", "Geo jautājums 5", "Cik ir 2+2?", "Cik ir 12+1?", "Cik ir 9+10?", "Kvadrātsakne no 49", "2+2=5?" };
 
     List<string> correctAnswer = new List<string>() { "3", "1", "2", "3", "1", "2", "2", "3", "1", "1" };
 
     public static string selectedAnswer;
 
     public Transform resultObj;
 
     public static string choiceSelected = "n";
 
     public static int randQuestion = -1;
 
     public int catMod = 0;
 
     public Transform auraObj;
 
     public float totalCorrect = 0;
 
     public float totalQuestions = 0;
 
     public Transform scoreObj;
 
     public float scorePer;
 
     public Transform nextButton;
 
     public Transform firstText;
     public Transform secondText;
     public Transform thirdText;
 
     public Transform firstChild;
     public Transform secondChild;
     public Transform thirdChild;
 
 
 
     void Start()
     {
         if (selectCat.catTopic == "Matemātika")
         {
             catMod = 5;
         }
 
         if (selectCat.catTopic == "Ģeogrāfija")
         {
             catMod = 0;
         }
     }
 
     void FixedUpdate()
     {
 
         //scoreObj.GetComponent<TextMesh>().text = "Score  :  " +totalCorrect;   nextButton.GetComponent<Transform>().position = new Vector3(28.8f, 8.62f, 0);
 
 
         if (totalQuestions > 0)
         {
             scorePer = (totalCorrect / totalQuestions) * 100;
         }
 
 
         scoreObj.GetComponent<TextMesh>().text = "Score  :  " + scorePer+ "%";
         if (randQuestion == -1)
         {
             randQuestion = Random.Range(0 + catMod, 5 + catMod);
 
             nextButton.GetComponent<Transform>().position = new Vector3(49.1f, 8.62f, 0);
 
             firstText.GetComponent<BoxCollider2D>().offset = new Vector2(-0.1f, 0.2f);
             secondText.GetComponent<BoxCollider2D>().offset = new Vector2(-0.1f, 0.2f);
             thirdText.GetComponent<BoxCollider2D>().offset = new Vector2(-0.1f, 0.2f);
 
             firstChild.GetComponent<BoxCollider2D>().offset = new Vector2(0.05347621f, -5.174473f);
             secondChild.GetComponent<BoxCollider2D>().offset = new Vector2(0.05347621f, -5.174473f);
             thirdChild.GetComponent<BoxCollider2D>().offset = new Vector2(0.05347621f, -5.174473f);
 
 
 
 
         }
 
         if (randQuestion > -1)
         {
             GetComponent<TextMesh>().text = questions[randQuestion];
             
         }
 
         //Debug.Log(questions[randQuestion]);
 
         if (choiceSelected == "y")
         {
             choiceSelected = "n";
             totalQuestions += 1;
 
 
             if (correctAnswer[randQuestion] == selectedAnswer)
             {
                 resultObj.GetComponent<TextMesh>().text = "Pareizi! Ejiet pa labi lai turpinātu";
                 totalCorrect += 1;
                 nextButton.GetComponent<Transform>().position = new Vector3(28.8f, 8.62f, 0);
                 firstText.GetComponent<BoxCollider2D>().offset = new Vector2(50f, 0.2f);
                 secondText.GetComponent<BoxCollider2D>().offset = new Vector2(50f, 0.2f);
                 thirdText.GetComponent<BoxCollider2D>().offset = new Vector2(50f, 0.2f);
 
                 firstChild.GetComponent<BoxCollider2D>().offset = new Vector2(50f, -5.174473f);
                 secondChild.GetComponent<BoxCollider2D>().offset = new Vector2(50f, -5.174473f);
                 thirdChild.GetComponent<BoxCollider2D>().offset = new Vector2(50f, -5.174473f);
 
             }
 
             else
             {
                 NextButton.resetAura = "n";
                 resultObj.GetComponent<TextMesh>().text = "Nepareizi!";
 
                 if (correctAnswer[randQuestion] == "1")
                 {
                     auraObj.GetComponent<Transform> ().position = new Vector3(-3.4f, 24.2f, 0);
                 }
 
                 if (correctAnswer[randQuestion] == "2")
                 {
                     auraObj.GetComponent<Transform>().position = new Vector3(9.9f, 24.2f, 0);
                 }
 
                 if (correctAnswer[randQuestion] == "3")
                 {
                     auraObj.GetComponent<Transform>().position = new Vector3(22.9f, 24.2f, 0);
                 }
 
                 nextButton.GetComponent<Transform>().position = new Vector3(28.8f, 8.62f, 0);
                 firstText.GetComponent<BoxCollider2D>().offset = new Vector2(50f, 0.2f);
                 secondText.GetComponent<BoxCollider2D>().offset = new Vector2(50f, 0.2f);
                 thirdText.GetComponent<BoxCollider2D>().offset = new Vector2(50f, 0.2f);
 
                 firstChild.GetComponent<BoxCollider2D>().offset = new Vector2(50f, -5.174473f);
                 secondChild.GetComponent<BoxCollider2D>().offset = new Vector2(50f, -5.174473f);
                 thirdChild.GetComponent<BoxCollider2D>().offset = new Vector2(50f, -5.174473f);
             }
         }
 
        
     }
 }