once we have the 5th slot in the garage, the rule states that we can pick up to 2 bonuses each time we park a car., even if the car is parked in one of the fourth first slots, right? Can I chose to rather take the 2 books bonus from slot 3 instead of 1 book+1 "something else" ?No + no. I don’t know where you’ve read that. The English rules are very clear on this (p 12 on the left):
No More Garages
If you already have all 5 of your garages occupied, then and only then, you can replace an old car, returning it to the supply; however, you don’t get to take the garage’s benefit again.