Please, help me translating these to C#

PhotonNetwork.Instantiate didn't work in JS. And there is no Scripting reference for C# (CodeAcademy noob here)

Here are two scripts

 var speed = 3.0;
 var sifaPrefab:Transform;
 
 function Update () 
 {
 // find out if button is pressed
 if(Input.GetButtonDown("Fire1"))
 {
     //check if has ammo
     if (collisions.SIFA_AMMO >0)
     {
         //create the prefab
         var sifa = Instantiate(sifaPrefab, transform.position, Quaternion.identity);
         // toss prefab
         sifa.rigidbody.AddForce(transform.forward * 2000);
         //remove ammo
         collisions.SIFA_AMMO -=1;
         print ("sifa dropped!");
     }
 }}

second script

 static var SIFA_AMMO=0;
 
 function OnControllerColliderHit(hit : ControllerColliderHit)
 {
     //check if colliding object is sifa
     if (hit.gameObject.tag == "sifa")
         {
             // destroy sifa
             Destroy(hit.gameObject);
             
             // add sifa to the inventory
             if (SIFA_AMMO == 0)
             {
                 SIFA_AMMO +=1;
                 print ("SIFA PICKED UP!");
             }                                    
         }
     }