I am a Mobile and API developer with variety of experience including Xamarin (C#) and Andriod Studio (Java). I create end to end solutions for mobile from API to User Interface.
Some Products / APIs I have worked with:
OneSignal Notification
Firebase
Stripe Payment Integration
Android and iOS SDKs
Google App Engine
Google Datastore
Google Drive API
OAuth by Google, Facebook etc.
Platforms: Xamarin Native, Xamarin Forms, Android Studio
Languages: C#, Java
So far I have helped many companies to successfully publish their Apps to Appstore (Google and Apple)