The main event is the Grand Parade of Cruise Ships. All the guest liners leave the city one by one with a colorful firework in the background. This looks incredibly beautiful on the advertising posters, but you need to understand that these photos were taken from the roofs of high-rise buildings, where not everyone can get access.
The Grand Parade takes place on Saturday during cruise days. Next date for cruise days you can find on the official website https://www.hamburgcruisedays.de/en/.
It is not easy to find a normal place on the promenade, as the number of spectators exceeds 500 thousand people, according to the organizers' estimates. In 2017 we watched the parade from the steps in front of Hotel Hafen Hamburg (N 53 32.786 E 9 58.141). You can also watch from the Stintfang viewpoint, which is nearby.
In 2023, we went up to the viewing platform at the Philharmonic, though the number of people was just huge and the first three rows were occupied even 2 hours before the start. That is, people came and stood there for two hours, holding a place. If you are ready to do the same, you can come here too.