[Transmission] Berlingo 1.6HDI-GEARBOX FAULT MESSAGE

[pankaj]

hi Guys,
i am a taxi driver and need help with my Berlingo 1.6hdi automatic(BERLINGO M-SP AIR VTR E-H)
bought the car which was a write-off (Year 2012 and Mileage on car is 5000 miles only), the car is not covered under warranty as it was repaired at a non-authorized Citroen garage.
i am having the below problem.
-while coming to a sudden stop the car misses gear and comes to neutral, i then have to move the gear to N and again put on Auto. Car also throws "Gearbox Fault" error on the screen while driving at low speeds(between 15-30 miles/hr)- any suggestions what could be the problem
- Second- where and how do i check the gearbox oil level
- Third- How do i change the gear oil
- Fourth- what oil is recommended, how much? and will be good to change the filter as well

Any suggestions and help is welcome. Thanks you.

[pankaj]

please reply- i need some help here

thanks