Simply yes, if you have your own hosting server, you can store your app data on your server's database. You just need to provide us your database API, so that we can access and store your app's data on your server.
If you do not have an existing hosting server. We can help you provide and set up it for you. Plus, our developers can create backend APIs to store your app's data. This work will cost you separately which will be estimated on the basis of web development pricing.