How can I fix. Please
how can I resolve that problem please
Hello~ Have you had you display replaced by someone other than Apple? If so the message will remain. If this is not your issue post back with more details. This is from the article you came from*
*An Unknown Part 
message will appear if the display installation is incomplete or if the display:
- Was replaced with a nongenuine display
- Was already used or installed in another iPhone
- Isn't functioning as expected
An additional message might appear that says "Apple has updated the device information for this iPhone." This means that Apple has updated the device information maintained for this iPhone for service needs, safety analysis, and to improve future products.
These messages don't affect your ability to use your iPhone.
Learn more about iPhone parts and service history.
~Katana-San~