The oil filled in the gearbox by the manufacturer should not be replaced. The oil level must be checked every 20,000 km.
To check the oil level, the oil temperature in the gearbox must be around +40°C. a Drive the car onto a flyover or into a viewing hole, make sure that the car is level.
Working under the vehicle, remove the filler plug (arrow above), oil should flow out slightly.
Add oil if necessary. The bottom arrow shows the oil drain plug.