Push Notifications — 2

I have an app built on the Android studio which uses messages sent from user to user who are registered on the Firebase database.
When a user receives a message on their phone through the app’s own internal chat, they get a notification from the app that a message has been received, so I need a push notification built into the app backend. please message for more details. Only sensible offers will be considered as I doubt it needs a lot of programming. Any offers over £40 will not be considered