3 oils in the gearbox

The Quatro A8 has three oils in the front drive.
1 in the differential
1 in the machine
and once again 1 quite behind, where the wave goes in the outside is driven along.
Where the shaft goes back into a housing
(probably Torsen) it is slightly moist.
Probably the Simmering is sweating (the gearbox is just 4 years old)
Can someone tell me where to get the last oil?
Oil level controlled?Where do you fill in?
You won't have to expand the gearbox at the end?

So long