HERTZ Car rental rip-off

I rented a vehicle from HERTZ at their Hamburg (Germany) central station office on 12 November 2019. I returned the vehicle the same day scratch-free and with a full tank. The rental was fully prepaid. Hertz froze EUR 360.00 as a security deposit. As I returned the vehicle after hours, no one was present and I dropped the keys in a security drawer as instructed when taking delivery of the car. When I received their final invoice the next day by email, I was astonished to notice that HERTZ had charged me with cleaning costs amounting to EUR 225.00 for a vehicle that needed to be washed as I drove it through rainy weather the day before.. My immediate complaint by email plus a reminder to respond to the initial email have not been responded to to date.