My display is original but .why Mu device shows this massage?

We, just users like you, can't do anything about that, since that's a normal behavior.

If you'd like, please submit your comments/requests/suggestions to Apple directly, using this link:--> Apple – Product Feedback - iPhone

Regards

Giulio

Carefully read this support article:--> About genuine iPhone displays

Regards

Giulio

Please re-read the last section of the support article I posted: "These notifications don’t affect your ability to use your iPhone or your display. You will see a notification on your Lock screen for the first 4 days that 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"

If you did not replace the display, then yes, something is wrong. It's a hardware problem that should be looked at by Apple.

If you did replace the display, and it was done by someone other than Apple or an authorized service provider, then yes, something is wrong and Apple won't touch that phone any more.

Did you receive this phone used? Did you purchase it from a phone company or Apple and it was new in a box? If you purchased it used and you got this message right away then the person who had it before you had the display swapped out and it is not a genuine Apple screen, or it wasn't replaced by Apple or a certified Apple repair center. The screen needs to be initialized to the logic board of the phone in order for that message to be removed and it has to be done by Apple or a Certified Apple repair center.

This is a hardware level issue, there is nothing that you are going to be able to do other than take it in to be serviced by Apple or a Certified Apple Repair center, but just from seeing the screenshot that you posted, the phone is not covered under warranty anymore so it's going to be costly to get that repaired. That is if Apple will even touch it anymore as it has been serviced by someone that is not certified to work on it.

It is not going to affect the usage of the phone as the screen may be an Apple display but was not swapped correctly when it was repaired and you are going to continue to get this message until some can physically reprogram the phone to use that display and math the display to the logic board.

In this case, it's a hardware failure.....You're going to need to take it in to have it serviced.