Why I phone is showing me this message about genuine

Did you have the screen replaced recently? If you did, the shop did not install the correct part. Take the phone back and have the correct Apple part installed.

You will know when the correct Apple replacement part is installed......the message about a non-genuine part will disappear.

You yourself cannot do anything. Only the Apple Store or an authorized Apple Service shop can install the correct part.

Unfortunately, because a non-authorized person has worked on the phone, Apple may decline to help at this point. Hopefully, that won't be the case.

No, it takes time for this notification to go away.

These notifications don’t affect your ability to use your iPhone or display.

You will see a notification on your Lock screen for the first four days you use your device and in the Settings app for 15 days. After that period, you can find the notification by going to Settings > General > About.

You can also update your IOS setting, which will help remove outdated notifications by going to Settings > General > Software Update to ensure your device has the latest update available.