Target API level specifications from August 2019
Your application is currently targeting API level 26. However, it must target API level 28 to a minimum in order to benefit from the latest APIs, which are optimized for security and performance.
As of August 2019, new apps will need to target Android 9.0 (API level 28) at a minimum.
Beginning in November 2019, application updates will need to target Android 9.0 (API level 28).
Change the target API level of your application
APK not optimized
This APK creates unused code and resources that are sent to users. You could reduce the size of your application with the Android App Bundle format. Because you do not optimize your application for device configurations, it is larger than necessary for download and installation on users’ devices. Large applications have lower installation rates and take up space on users’ devices.
Use the Android App Bundle format to automatically optimize your app for device configurations, or manage it yourself with multiple APKs.