I created a social network, and I implemented notifications in it. However, I can not find an effective way to send site notifications (tastings, comments, messages) via push notifications to the android app. I configured the firebase, the onesignal, and the application receives test pushs, but how do I send these notifications that are on my server to a mobile device? I know I need Firebase for this, but how do I send server notifications to firebase? Can anyone give me a light? I have been on this project for months and I can not seem to get out of the blue.