I paid an extra 30 euros for an upgrade and the car was excellent and good value for money

You did very well!

I was surprised that we rented a car from Goldcar through this system despite trying to avoid them like the plague as we had a very bad experience with Goldcar in the past. I guess this is just a way for them to trick people into renting with them. That said, we had a good experience this time around

I should pay by the take over the amount of 66 eur. It was charged imediatelly.

There were a lot of hidden costs that we were not informed about upfront, including a mandatory €1000 deposit if we didn't pay out for the extra insurance cover, and a €102 fuel deposit (which is more fuel than will even fit in a Fiat 500). Staff also didn't tell us about these costs in one go, even when directly asked 'what is the total we will have to pay'. This created a really negative experience for us and impacted on a lot of our holiday plans. It seemed like this was intentional, a way of forcing people into paying money without giving them the full information in advance, and it felt like we were being scammed. It was also contrary to the information that we received from our broker, Easyrentcars.com, which advised that we could be charged a maximum deposit of up to the equivalent of $500, meaning that we were missold this car hire deal. In future I will avoid Interrent and recommend that others do also.