Implement some extra services in an android studio project

Hello guys, I have a webview app in an android studio project and I want to implement some services in the app in order to work as it is already happening on the web. The services are: 1. Geolocation tracking 2. Filepicker function ( The function is already developed but the app needs the proper service in order to access it) 3. Background service ( I want the app to run in the background even if the user close it ) The above services are not a big job for someone who is experienced. The developer will send me the code and some instructions in order to make it by myself.