The games created for android are so slow that the app closes

The games created for android are so slow that the app closes. How can i create mobile games that run smoothly, i have android 6.0 and 3gb ram

Hmmm…Android 7 replaced Android 6 over 6 years ago. Android 6 is less than 3% of all devices still connecting to the mobile stores from some quick checks.

You should try the web demo and see any of the examples run properly in browser. Game examples and templates made with GDevelop | GDevelop

I’d recommend using Not-a-vania or the new platformer example as they use most of the standard features of the engine.
If those don’t run well on your phone, I’d be willing to bet your device doesn’t support the current version of WebGL and therefore is outside of the minimum specs to run the games from the engine efficiently.