Solution 1 :
You must use online databases.
- Firebase Realtime Database
- Firebase Firestore
- Azure SQL Database
Or you can host a database & server to serve your requirements.
If the customer places their order an app, it affects the SQLite database in their phone and I think the SQLite database is separate for every phone.
Then how can I get their order in the seller’s phone app?
Can I use other than SQLite for maintain one database?
Comment posted by Ryan M
You’ll need to create some sort of backend that syncs all this.