Hi Madge, and welcome to cruise-chat.
As your flight is in the evening, you will debark the ship after most other passengers. All passengers are assigned a "color tag" based on a number of factors, including flight time. The color system is used to get people off the ship in as orderly a fashion as possible. You will also use this color to locate your luggage after debarking.
On Celebrity, you will be assigned a waiting area onboard based on your assigned color. When it is your turn to disembark, a crew member will enter the room to let you know, and then escort the group to the gangway.
I'd estimate that it will be at least two hours between the published time of arrival and the time you actually get off the ship. You can use this time to have a nice, leisurely breakfast.
Yes, you will also have a long wait at the airport, but it would probably be from about noon on.
Another option might be to take a shore excursion offered by the cruise line on disembarkation day...typically a tour of the surrounding area. These are offered only to those pax with late flights, but I don't know if that includes international flights.
Some passengers will opt to spend the day at a hotel. They take a taxi from the pier to a hotel nearby, enjoy the day at the pool, and then take a taxi to the airport a few hours before the flight. But...you will still he among the last ones off the ship due to the time of your flight, so it will be at least noon before you are checked into the hotel.
Hope this helps somewhat.