Try a codelab
Google Developer Codelabs provide short, guided coding experiences. Google I/O 2017 featured several Firebase-focused codelabs.
Codelabs are free, self-paced, online modules.
Level: Intermediate to Advanced
Learn how to add Firebase Analytics to your app and use it to make informed decisions about things like ad placement, products to stock, and how difficult to make a level in a game.
Firebase in a Weekend
Learn to use Firebase to build and scale your apps. Implement the Firebase Realtime Database and learn how to set up authentication, notifications, remote configuration, and analytics.