Terrible and I wish I had went with another company

I was very disappointed in my recent rental service with EuropCar. Its the first time I've used Europcar. It took me half an hour standing at the counter before I could even sign my document. A group that came 20 minutes after me had received their car in 10 minutes, and they also had an additional driver form to sign. I was a single driver, and the Europcar person that I was dealing with just made me wait, saying that his computer was slow. However, no effort was made to move me to the other computer, and there was no sense of urgency towards giving me my keys. He was humming throughout the entire process, showing that he was not in a hurry. I have rented cars many times, and it usually takes me 10 minutes at most to acquire a set of keys. Further, I did not receive any documentation or a receipt. He had also asked me for my card twice, even though he had charged me once. 30 minutes is a very long time to wait before even signing any documents. I received an 'upgrade' from a small car to a small SUV. However, upon getting to the car, it had a car seat, which I did not request for. This took up space in the car. At the counter, I was told a staff member would be near the car park if I needed to speak to him. However, there was nobody there. Because I had been waiting 30 minutes at the counter, I decided to just take the car. The inside of the car was not clean. There was sand and dirt all over the floors of the front passenger seat. Attached is a photo. I also received no documentation on my car rental agreement, so I do not have any details on the car rental itself. I made a complain to the same staff member when returning the keys, and did not hear back even after a week. In the time that I had been waiting at the counter, my fees and liabilities were not explained to me. Overall, it had been a very frustrating experience with EuropCar. I'd like to suggest better training of staff, and a higher standard of customer service.