It’s been a while since I regularly used a car, but I remember the automatics my father had having some sort of logic that shifted up when driving at a constant speed, than back down when wanting to accelerate.
Now those where fancy pants Systems (I think they called them 7G-Tronic), but this was also over 10 years ago, and such logic doesn’t strike me as overly complicated, so I’m surprised there’s current cars with static shift speeds.
You don’t. Autobahnen usually exist between cities, and are separate from other types of traffic. Your vehicle also needs to meet a minimum speed requirement to be allowed on. When an Autobahn runs through a city, there’s usually a grade separation.