How to change the speed of gameobject?

Hi guys, i have some problems with this script: (read down for why..)

     var cameraObject : GameObject;
  @HideInInspector
  var targetXRotation : float;
  @HideInInspector
  var targetYRotation : float;
  @HideInInspector
  var targetXRotationV : float;
  @HideInInspector 
 var targetYRotationV : float;
 
 var rotateSpeed : float = 0.3;
 
     var holdHeight : float = -0.5;
  var holdSide : float = 0.5;
  var racioHipHold : float = 1;
  var hipToAimSpeed : float = 0.1;
  @HideInInspector
  var racioHipHoldV : float;
 
 var aimRacio : float = 0.4;
 
 var zoomAngle : float = 30;
 
 

    var fireSpeed : float = 15;
  @HideInInspector
  var waitTilNextFire : float = 0;
  var bullet : GameObject;
  var bulletSpawn : GameObject;
 
     var shootAngleRandomizationAiming : float = 5;
  var shootAngleRandomizationNotAiming : float = 15;
 
 var recoilAmount : float = 0.5; 
 var recoilRecoverTime : float = 0.2;
  @HideInInspector
  var currentRecoilZPos : float;
  @HideInInspector
  var currentRecoilZPosV : float;
 
 var bulletSound : GameObject; 

 var muzzelFlash : GameObject;
 
 function Update () { 
 var holdMuzzelFlash : GameObject;
  var holdSound : GameObject;
  if (Input.GetButton("Fire1")) { 
 if (waitTilNextFire <= 0) { 
 

    if (bullet)
  Instantiate(bullet,bulletSpawn.transform.position, bulletSpawn.transform.rotation);
  if (bulletSound)
  holdSound = Instantiate(bulletSound, bulletSpawn.transform.position, bulletSpawn.transform.rotation);
  if (muzzelFlash)
  holdMuzzelFlash = Instantiate(muzzelFlash, bulletSpawn.transform.position, bulletSpawn.transform.rotation);
 
  targetXRotation += (Random.value - 0.5) * Mathf.Lerp(shootAngleRandomizationAiming, shootAngleRandomizationNotAiming, racioHipHold);
  targetYRotation += (Random.value - 0.5) * Mathf.Lerp(shootAngleRandomizationAiming, shootAngleRandomizationNotAiming, racioHipHold);
  currentRecoilZPos -= recoilAmount;
 

     waitTilNextFire = 1; 
       } 
    }
  waitTilNextFire -= Time.deltaTime * fireSpeed;
     
     if (holdSound)
         holdSound.transform.parent = transform;
     if (holdMuzzelFlash)
         holdMuzzelFlash.transform.parent = transform;
     
     currentRecoilZPos = Mathf.SmoothDamp( currentRecoilZPos, 0, currentRecoilZPosV, recoilRecoverTime);
     
     cameraObject.GetComponent(MouseLookScript).currentTargetCameraAngle = zoomAngle;
     
     if (Input.GetButton("Fire2")){
         cameraObject.GetComponent(MouseLookScript).currentAimRacio = aimRacio;
         racioHipHold = Mathf.SmoothDamp(racioHipHold, 0, racioHipHoldV, hipToAimSpeed);}
     if (Input.GetButton("Fire2") == false){
         cameraObject.GetComponent(MouseLookScript).currentAimRacio = 1;
         racioHipHold = Mathf.SmoothDamp(racioHipHold, 1, racioHipHoldV, hipToAimSpeed);}
     
     transform.position = cameraObject.transform.position + (Quaternion.Euler(0,targetYRotation,0) * Vector3(holdSide * racioHipHold, holdHeight * racioHipHold, 0) + Quaternion.Euler(targetXRotation, targetYRotation, 0) * Vector3(0,0,currentRecoilZPos));
     
     targetXRotation = Mathf.SmoothDamp( targetXRotation, cameraObject.GetComponent(MouseLookScript).xRotation, targetXRotationV, rotateSpeed);
     targetYRotation = Mathf.SmoothDamp( targetYRotation, cameraObject.GetComponent(MouseLookScript).yRotation, targetYRotationV, rotateSpeed);
     
     transform.rotation = Quaternion.Euler(targetXRotation, targetYRotation, 0);
     }
     
     //cameraObject.GetComponent(MouseLookScript).currentTargetCameraAngle = zoomAngle;

Is there any way i can change the speed of bullet? This script has been taken from FPS project,(dont remember name) and i want to change the speed of my bullet. Bullet is prefab and Instantiates as clone when mouse button 0 is pressed. The speed needs to be changed because now its unlimited, literally. I cant hit the object with that speed, it flies through. And heres the Collision script:

 function OnTriggerEnter(other : Collider) {
 
 if(other.CompareTag("Enemy"))
 
     print("Enemy is hit!");
 
     Destroy(other.gameObject);  
 }

It doesnt detect the collision. Please tell me how it can detect the bullet collision and destroy the collided object. This second script is attached to my bullet prefab.

Thanks.