Automatic automatic transmission problems

Good afternoon

I have a Mercedes class A automatic, and I have problems with transmission since it seems to drip fluid at the bottom, none of the positions of the gearbox works.

I would like to know how to replace transmission liquid, it does not seem possible, since in the manual it can only do the official Mercedes service. Is there any method of doing it?

And if someone has the workshop manual of this car.

Thank you so much