after enabling Hermes I see the performance increase but the size of the app increase by 1.3Mb so there is any way to make the size smaller?
On iOS, using Hermes will necessarily make the app bigger.
This is because React Native iOS will by default use the platform's built-in JavaScript interpreter instead of bundling its own. When you use Hermes, you are adding a JSVM to the app where there wasn't one before, increasing the size.
Android does not have a platform JSVM, so React Native always ships one. When you enable Hermes on Android, you are replacing one JSVM with another, so the size difference is smaller and likely negative.