Hi,
I am expert in Android [ kotlin ], [ java ], [ Flutter ] apps working with quite a few years,
I have read your project proposal.
I can update your Android [ Java ] app from sdk 15 to current in accordance with your needs.
It seems we need to discuss in detail about requirements. Share the source code of your app to update it with new version.
So, it's would be extendable latter if you want to add new functionality in your app.
I will provide you a quality work.
Let's chat to proceed.