Typing Hero needs to run in background all the time so it can detect keyword whenever you type.
Modern Android system has built-in mechanism to preserve battery life called Doze.
When you start Typing Hero for the first time, Typing Hero asks to be excluded from Doze to ensure it can run background all the time.
Unfortunately, some manufacturers take battery optimization to a whole new level, in a bad way.
To preserve battery life, manufacturers add additional battery optimization mechanism that aggressively kills apps running in background.
On Xiaomi devices, apps cannot even run automatically when the device is starting up.
Typing Hero is likely killed by the system if you are experiencing one of these.
Here are the general ideas on how to let Typing Hero run in background all the time regardless of what device you use.
Please follow the links below to configure your device properly so Typing Hero can run in background all the time.