Yes. Even after completing the pre-registration, you still need the passify app when you arrive at the terminal.
Here is what happens at the gate:
Open the app and select C. Steinweg (SWT) as your terminal.
Tap Check-in and select your slot.
The app displays your Slot ID, which you show to the staff at the gate window.
Your company's collection authorisation is verified via German Ports. If everything is in order, you can proceed with your tour.
Once your tour is complete, don't forget to check out in the app as you will not be able to check in for a new tour until you do.