[HELP] Joystick Movement/Button Movement

Im trying to make my 3rd person game work when I press buttons to move my character just as I would with my WASD Control.. but he either goes through the terrain or wont move at all.. please and thank you!!

 #pragma strict
 public var walk = false;
 public var attack = true;
 var speed : float = 1.0;
 var rotateSpeed : float = 3.0;
 var walkspeed: float = 5.0;
 
 function Start () {
 
 }
 
 function Update () {
 if (Input.GetButtonDown ("UP")) {
                      var move: Vector3 = Vector3.forward * 4.0;
 
     transform.Translate(move * Time.deltaTime);
         }
 }
 
  function Slap ()
   {
   attack = true;
 animation.Play("bitchslap",PlayMode.StopAll);
 yield WaitForSeconds(0.75) ;
  attack = false;
   }
   
 function OnGUI() {
         //SLAP Button
         if(GUI.Button (new Rect(Screen.width / 2 + 100, Screen.height / 250 + 170 + (10 * 25), 100, 50), "Slap")) {
          StopCoroutine("Slap");
         StartCoroutine("Slap");
         }
         
         //JUMP Button
         if(GUI.Button (new Rect(Screen.width / 2 - 90, Screen.height / 250 + 170 + (10 * 25), 160, 50), "JUMP")) {
          animation.Play("jump");
     rigidbody.AddForce(Vector3.up *speed);
         }
         
         //MOVEUP Button
         if(GUI.Button (new Rect(Screen.width / 2 - 250, Screen.height / 250 + 90 + (10 * 25), 50, 50), "UP")) {
         animation.Play("walk");
 
         
         }
         
         //MOVEDOWN Button
         if(GUI.Button (new Rect(Screen.width / 2 - 250, Screen.height / 250 + 150 + (10 * 25), 50, 50), "DOWN")) {
         animation.Play("walk");
         
         }
         
         //MOVERIGHTButton
         if(GUI.Button (new Rect(Screen.width / 2 - 190, Screen.height / 250 + 120 + (10 * 25), 50, 50), "RIGHT")) {
         animation.Play("walk");
         }
         
         //MOVELEFTButton
         if(GUI.Button (new Rect(Screen.width / 2 - 310, Screen.height / 250 + 120 + (10 * 25), 50, 50), "LEFT")) {
         animation.Play("walk");
         
         }
     }