There are multiple reasons why a game can crash. Please follow the steps below.

1. Turn off all applications running in the background, apart from NEW STATE MOBILE
2. Check the version of your OS and update to the latest version if necessary
3. Check your network (Wi-Fi/data) connection
4. Change the graphic settings on NEW STATE MOBILE
5. Clear your game cache: [Settings -> select 'NEW STATE MOBILE' -> Storage -> Clear all data and cache]