A game crash is most commonly caused by a lack of memory on your device. However, sometimes disconnections and other issues can be caused by a poor connection.
Before taking any other steps, make sure that your game is updated and your device uses Android 5 or above or iOS 10.0 or above.
We strongly recommend that the game is played on a device with at least 1 Gigabyte of RAM available.
Ensure that you're playing on a stable network connection.
If you've checked the list and the device meets the above requirements, the next best step is to restart your device.
You can also try uninstalling then reinstalling the game. Before doing this, please make sure you've connected your game to either Google or Apple Sign In to save your game progress.