i want to make may 20 question randomize plss help its for may baby thesis :D thx

using UnityEngine; using UnityEngine.UI; using UnityEngine.SceneManagement; using System.Collections;

public class responder : MonoBehaviour {

 public int idtema;

 public Text pergunta; //pergunta means question//
 public Text btnA;
 public Text btnB;
 public Text btnC;
 public Text btnD;
 public Text inforepostas;

 public string[] perguntas;
 public string[] alternativeA;
 public string[] alternativeB;
 public string[] alternativeC;
 public string[] alternativeD;
 public string[] correct;

 private int idPergunta;

 private float Answering;
 private float question;
 private float media;

 // Use this for initialization
 void Start () {
     idPergunta = 0;
     question = perguntas.Length;


     pergunta.text = perguntas [idPergunta];
     btnA.text = alternativeA [idPergunta];
     btnB.text = alternativeB [idPergunta];
     btnC.text = alternativeC [idPergunta];
     btnD.text = alternativeD [idPergunta];

     inforepostas.text = " Answering " + (idPergunta + 1).ToString()+ " of " + question.ToString ()+"questions.";
 }
 

 public void btn(string alternative)
 {
     if(alternative == "A")
     {
         if (alternativeA[idPergunta] == correct [idPergunta])                                     //EXECUTE A COMMAND FOR ANSWER A
         {                          
             Answering += 1;

         }
     }

     else if(alternative == "B")
     {
         if (alternativeB[idPergunta] == correct [idPergunta])
         {                          
             Answering += 1;
         }
     }

     else if(alternative == "C")
     {
         if (alternativeC[idPergunta] == correct [idPergunta])
         {                          
             Answering += 1;
         }
     }

     else if(alternative == "D")
     {
         if (alternativeD[idPergunta] == correct [idPergunta])
         {                          
             Answering += 1;
         }


     }
     idtema = Random.Range (0, 9);
     proximaPergunta();
 }



 void proximaPergunta()
 {
     idPergunta += 1;


     if (idPergunta <= (question - 1)) {


         pergunta.text = perguntas [idPergunta];
         btnA.text = alternativeA [idPergunta];
         btnB.text = alternativeB [idPergunta];
         btnC.text = alternativeC [idPergunta];
         btnD.text = alternativeD [idPergunta];


         inforepostas.text = " Answering " + (idPergunta + 1).ToString () + " of " + question.ToString () + "questions.";
     } else
       {
         SceneManager.LoadScene ("Result1");

     }


 }

}