How to save my progress? The only way to secure your progress and make sure you never lose it is to connect your game to Facebook,
The Angry Birds 2 save data “link” is but a cloud sync feature tied to Facebook, Apple ID, or Google Play Games. Players must link their game to one of these services before switching devices. No manual save file transfer is supported or safe. For complete protection, link at least one account method and keep a screenshot of your User ID. angry birds 2 save data link
Before you try to fix anything, it is important to understand how the game saves your data. How to save my progress