I can't download any .APK file in my Android phone. Can anyone solve the problem?

By following these steps your problem should be solved: 

1. Install bundles with the help of an app. Not all APKs are available using Android Package Installer.
2. Do a clean install instead of updating.
3. Check to see if you have enough storage space.
4. Allow installation from unidentified sources.
5. Check that the APK file isn't corrupted or missing.