There should be totally 9,7 litres of oil in that transmission and usually it should come out about half of it from the sump if the oil was not low in the box, 2 litres out and 3 in doesnt sound good enough to me. To refresh the oil well you have to change it at least 2 times consecutively which means after you changed it first go for a ride as the box to go several times through all gears to mix well all the oil then change it again, this way the oil will be about 80% refreshed, adding 3 litres of fresh oil to a capacity of 9,7 litres is just a botch, less than 1/3 of the oil is fresh this way.