This does not happen on other devices from what I've tested.
possible solutions:
1. Your device might be out of memory and eventually crash the game - you might want to make sure that less apps are running in the background while you play.
2. You might want to try a different platform? Windows / Mac / Linux
3. You might be out of storage space, if so, removing a few things from the phone and trying again might help.
4. Unlikely to solve anything, but you might want to restart the device and try again
More information ? :
What device are you using? Is there an error that you see when it happens? Does the game freeze or just close the app? Does it happen with other games too / or the free version?