Android service that gets data from firebase databse

Question

I am making a chat app and I am trying to make message notification. I have a Firebase database that i store all my data (users, friends, messages). When user sends a message, app adds that message to firebase database ( path is "/notification/user_who_recived/user_who_send" ).

my problem is i cant make service that gets message in "/notification..../" path and makes notification based on message.

here is my test code that doesnt work:

package com.cagsak.chatapp

import android.app.PendingIntent
import android.app.Service
import android.content.Context
import android.content.Intent
import android.os.IBinder
import androidx.core.app.NotificationCompat
import com.google.firebase.auth.FirebaseAuth
import com.google.firebase.database.FirebaseDatabase


class background_service : Service(){
    override fun onStartCommand(intent: Intent?, flags: Int, startId: Int): Int {

        println("background_service: THREAD İS STARTED")
        val uid = FirebaseAuth.getInstance().uid ?: stopSelf()
        val ref = FirebaseDatabase.getInstance().getReference("/notifications/$uid")
        ref.get()
            .addOnSuccessListener { data_list ->
                println("background_service: MESSAGE GETTING IS SUCCESSFUL")
                data_list.children.forEach { child ->
                    val data = child.getValue(ChatMessage::class.java)
                    if (data != null) {
                        println("background_service: MESSAGE RECEIVER IS FOUND")
                        SendNotification(data, baseContext)
                        child.ref.removeValue().addOnSuccessListener {
                            println("background_service: MESSAGE DATA IS DELETED")
                        }
                    }
                }
            }


        return START_STICKY
    }

    override fun onBind(intent: Intent?): IBinder? {
        return null
    }

    private fun SendNotification(message: ChatMessage, context: Context) {
        FirebaseDatabase.getInstance()
            .getReference("/users").get()
            .addOnSuccessListener { userlist ->
                userlist.children.forEach { user_data ->
                    val user = user_data.getValue(User::class.java)
                    if (user != null && user.uid == message.fromId) {
                        val intent = Intent(context, ChatMessage::class.java)
                        intent.putExtra("USERKEY", user)
                        val pendingIntent: PendingIntent =
                            PendingIntent.getActivity(context, 0, intent, 0)

                        NotificationCompat.Builder(context, "MY_CHANEL_ID")
                            .setSmallIcon(R.drawable.small_logo)
                            .setContentTitle(message.fromId)
                            .setContentText(message.text)
                            .setPriority(NotificationCompat.PRIORITY_HIGH)
                            .setContentIntent(pendingIntent)
                            .setAutoCancel(true)
                            .build()
                    }
                }
            }
    }
}