Mercedes Automatic Automatic Changes A170

good afternoon everyone.

I have a problem in the automatic gearbox of a Mercedes type at 170 of diesel.
It turns out that the witness of the painting changes, where the \ "d \" marks to go automatically and change to \ "f \", that I do not know what it means, what happens is that the gearbox fails and the engine loses all the power and does not change or accelerate. I hope someone can help me, thanks

Hello a query the engine or the box, because if the engine loses power the box does not work? Why if the engine already said when we miss pecity begins to revive the change. A Abraco