update recyclerview in real time after firebase delete

Question

I have an app with recyclerview with the option to edit and delete the items from the list. when I delete or update one of the items it gets updated or deleted successfully from the realtime database in firebase but for some reason, in the recyclerview it duplicates the item and I need to rest the activity in order to see the change currently. that is unless there is only one item in the list then it works as expected.

the activity to show the recylerview:

private  lateinit var dbref: DatabaseReference
private  lateinit var userRecyclerView: RecyclerView
private  lateinit var userArrayList: ArrayList<User>

private fun getUserData(){
    dbref = FirebaseDatabase.getInstance().getReference("Users")
    dbref.addValueEventListener(object :ValueEventListener{
        override fun onDataChange(snapshot: DataSnapshot) {

            if(snapshot.exists()){
                for(userSnapshot in snapshot.children){
                    val user = userSnapshot.getValue(User::class.java)
                    userArrayList.add(user!!)
                }

                userRecyclerView.adapter = MyAdapter(userArrayList)
            }
        }

        override fun onCancelled(error: DatabaseError) {

        }


    })

}

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_list)

    userRecyclerView = findViewById(R.id.userlist)
    userRecyclerView.layoutManager = LinearLayoutManager(this)
    userRecyclerView.setHasFixedSize(false)


    userArrayList = arrayListOf<User>()
    getUserData()

onBindViewHolder:

override fun onBindViewHolder(holder: MyViewHolder, position: Int) {
    val currentUser = userList[position]

    holder.username.text = currentUser.name
    holder.app.text = currentUser.app
    holder.password.text = currentUser.password

delete:

holder.delete.setOnClickListener(){
        val builder = AlertDialog.Builder(holder.itemView.context)
        builder.setMessage("Are you sure you want to Delete?")
            .setCancelable(false)
            .setPositiveButton("Yes") { _, _ ->
                // Delete from firebase
                val  db = FirebaseDatabase.getInstance()
                val ref = db.getReference("Users")
                ref.child(currentUser.id.toString()).removeValue().addOnCompleteListener(){
                    userList.removeAt(position)
                    notifyItemRemoved(position)



                }
            }
            .setNegativeButton("No") { dialog, _ ->
                // Dismiss the dialog
                dialog.dismiss()
            }
        val alert = builder.create()
        alert.show()
    }

update:

 val user = mapOf(
                "app" to holder.app.text.toString(),
                "name" to holder.username.text.toString(),
                "password" to holder.password.text.toString()
            )
            val  db = FirebaseDatabase.getInstance()
            val ref = db.getReference("Users")
            ref.child(currentUser.id.toString()).updateChildren(user).addOnSuccessListener(){
                notifyItemChanged(position)
            }