Educational Android App Development

I need an end-to-end Android application built for students that serves a clear educational purpose. The core flow should open with streamlined user authentication—Google, email, or phone sign-in are all acceptable as long as the solution is secure and follows current Android guidelines. Once logged in, learners will browse course material, quizzes, or other learning modules.

Some content must sit behind a paywall, so please wire in-app purchases using Google Play Billing. This should cover one-time payments as well as the option to unlock bundles of premium lessons. The purchase flow has to feel native and restore entitlements reliably when the user reinstalls or switches devices.

I am happy with either Kotlin or modern Java, but the project needs to be built in Android Studio and integrate a reasonable back-end stack—Firebase Firestore or your preferred alternative—for user data, progress tracking, and purchase receipts. Clean architecture, material-compliant UI, and well-commented code are essential because I intend to maintain and expand the app after launch.

Deliverables:
• Signed release-ready APK and Play Console artefacts
• Complete source code with build instructions
• Brief setup & maintenance guide (PDF or Markdown)

I will consider the job complete when I can compile the project locally, sign in as a test user, make a sandbox purchase, and see the correct entitlement unlocked. If you have shipped similar educational apps before, please mention them so I can quickly gauge fit.