I dropped my Maxi-Cosi Rodi (fix) (SPS, XP, AirProtect) car seat on the ground. Do I have to replace it now?

No, that is not necessary if it was a normal ‘drop’ and not an extremely hard one or from a considerable height. When a car seat is dropped on the ground, it is not subject to the same kinds of forces as are exerted during a (serious) collision. There is therefore no need to replace the car seat.