You can easily report soiling and damage here.
FAQ
Carsharing
The stickers show you which car sharing providers are authorised to use the hvv switch point. Use may vary depending on the provider and location: If the hvv switch point is located within the business area of the car sharing provider, the rental can be started, ended and also temporarily stopped there. If the hvv switch point is outside the business area, you can only stop temporarily. Your current rental cannot then be cancelled. With cars from the station-based car sharing provider Dorfstromer, you can stop off anywhere, regardless of the sticker.
Tip: The business areas of MILES, SIXT share and SHARE NOW are displayed in the hvv switch app once you have selected a car.