Transmission and hydraulic oil

Well, it's almost two years since I got the V8. It's a Bj. 89, with now nearly 270,000 km. In the last two years, there was no need for large investments except for normal wear parts (brakes, timing belts and a few other small items). The problem with my squeaky ventilation I managed to solve with the Ballistol spray. I had a few rust spots removed, unfortunately the rear sheet metal on the trunk annoys me even further ;-). The driving performance is m.E. for the weight really outstanding and I am always happy to turn around the ignition key.

But now I have a few questions for the experts here in the forum, maybe some of them can give me some tips.

1. The gearbox loses oil easily. How can I remedy this? I have an oil measuring rod from the previous owner in the engine compartment. I can measure here, but how do I know how much I need to be in it? Can this be checked for itself and how is the filling done? Can I do this over the stub where I have the measuring rod, say fill in directly?

2. The vehicle loses slightly hydraulic oil (approx. ==References== I followed the lines in the engine compartment and found that the "coupling components" were light, really light. How can I deal with this?