Reservation and pick up is OK. I will be back here when I drop off.
Drop off, like the pick up was easy. The service can be better though. During pickup, Sixt workers ought to take customers to the vehicle for joint inspection of the state of the vehicle and a some instructions on how the vehicle operates.
Also, at drop off, workers need to inspect the vehicle in the presence of the customer to clarify the state of the vehicle.
Leaving these undone gives room to the company to defraud customers with complaints of damages to the car when none exists.
This didn't happen to me, but I think it will help to secure the integrity of the company and earn the trust of the customers.