Fuel surcharge upon car drop-off

When picking up the car at Queenstown Airport a closer to 9pm, we waited for 20+ minutes before being served. The counter lady is a trainee and told us that we have to find the car ourselves as she does not know which bay# the car resides. Also she could not answer some of the questions on card authorisation and insurance which leaves us quite unhappy. We finally found the car we noted that the petrol was not entirely full and it is not upon drop-off that we got told that we have to take a photo to validate such. Without any further info from the trainee, we simply infer that we need to return the car at the same petrol level to when we pick it up. So we filled up the petrol to full tank before we drive out from our final destination to Christchurch airport which took one hour and return the car as it is. During the rental we also notified Europcar that the electric uplift back door malfunction at times. Later we received an invoice from Europcar and got charged additional 86NZD on petrol which left us extremely unsatisfactory about the entire rental experience.