1999 Opel Astra G 2.0DTL Gearbox: Drain Plug Location, Inspection & Oil Filler Plug Questions

Hello, I have an Opel Astra G 2.0DTL from 1999. Reverse thrust to the rear. I have a few questions about the gearbox in this car. Where is the drain plug? Is it at the lowest point near the sledge here:


And where is the inspection and oil filler plug? Is he here on the driver's side? This place is marked in the photo:


Or maybe somewhere near the reverse gear sensor?

https://obrazki.elektroda.pl/5599739100_1502392746.jpg

Buddy, thanks a lot for explaining what, where and how. Do you have any more drawing showing the complete structure of such a box? Or is there a program where I can find it?

In addition, I wanted to ask what oil is poured into such a gearbox and how much more or less goes there?
And maybe colleagues know which places can most often leak from this chest? I don't think it's flying from the sealants. It kind of flies from the drain plug, is there a gasket or a copper washer? Maybe she is failing? It is definitely oil from the box because it is red in color.