Can somebody help me please?

using UnityEngine;
using System.Collections;

public class NumberWizards : MonoBehaviour {
// Use this for initialization
int max;
int min;
int guess;

void Start () {
	startgame();
}

void startgame () {
	int max = 1000;
	int min = 1;
	int guess = 500;
	
	max = max + 1;
	
	print ("========================");
	print ("Welcome to number wizard");
	print ("Think of a number in your head, but dont tell me!");

	print ("The highest number you can pick is" + max);
	print ("The lowest Number you can is" + min);

	print ("Is your number higher or lower than" + guess);
	print ("Up = higher, lower = down, return = equal");
}

	// Update is called once per frame
	void Update () {
		if (Input.GetKeyDown(KeyCode.UpArrow)) {
			min = guess;
			NextGuess();
		} else if (Input.GetKeyDown(KeyCode.DownArrow)) {
			max = guess;
			NextGuess();
	    } else if (Input.GetKeyDown(KeyCode.Return)) {
			print("I won!");
		}	
    }

	void nextguess () {
		guess = (max + min) / 2;
		print ("Higher or lower than" + guess);
		print ("Up = higher, lower = down, return = equal");
	}
}

@liibanhassan13
keep your ints out side of voids

using UnityEngine;
 using System.Collections;

public class NumberWizards : MonoBehaviour { // Use this for initialization int max; int min; int guess;
public int max = 1000;
        public int min = 1;
        public int guess = 500;
     void Start () {
         startgame();
     }
     
     void startgame () {
        
         
         max = max + 1;
         
         print ("========================");
         print ("Welcome to number wizard");
         print ("Think of a number in your head, but dont tell me!");
     
         print ("The highest number you can pick is" + max);
         print ("The lowest Number you can is" + min);
         print ("Is your number higher or lower than" + guess);
         print ("Up = higher, lower = down, return = equal");
     }
         // Update is called once per frame
         void Update () {
             if (Input.GetKeyDown(KeyCode.UpArrow)) {
                 min = guess;
                 
             } else if (Input.GetKeyDown(KeyCode.DownArrow)) 
                 max = guess;
                 
              else if (Input.GetKeyDown(KeyCode.Return)) 
                 print("I won!");


               
         }
       
         void nextguess () {
             guess = (max + min) / 2;
             print ("Higher or lower than" + guess);
             print ("Up = higher, lower = down, return = equal");
         }
      }