If you are changing from Android to iOS or vice versa, please follow these instructions:

In terms of transferring game progress, the only bridge between Android and iOS device is 'Facebook'. That means you should bind your main game progress to a Facebook account at least. First, please update the game to the newest version on both devices in case of unexpected issue.

1 - Download the game on your new device: a new game process will start automatically.

2 - Login your previous Facebook account on the new device.
3 - Follow the tutorial until the end.
4 - Go to settings, and then you will be able to switch to your old account under the option 'Switch Accounts'.

5 - Choose 'Facebook' to switch back to your main game process.