German transportation in all its many forms is modern and effective, although the rail system has more delays than it used to thanks to failed cost-cutting measures. Cities generally have useful transport apps, ticket machines in English, and allow you to use one ticket to take all forms of transport (including regional trains making stops within a city) for a certain amount of time. In Berlin, a one-time transit ticket covers travel in one direction for two hours. Cities generally have large streetcar networks, as well as subways (“U-Bahn”) and light rail (“S-Bahn”). Taxi apps aren't so common, other than Uber in Berlin and Munich. Major cities are linked by regular, high-speed trains.
Recent efforts to introduce speed limits on the entire Autobahn failed spectacularly, although a large proportion of the expressways do have speed limits. We tend to recommend against using rental cars in Germany, as Central European rental agencies charge steep fees for drivers picking up a car in one country and leaving it in another, and German city centers are not designed for cars. If renting, take seriously the advice given by a rental agency for driving on the Autobahn. Stay out of the leftmost lane, and if you encounter a traffic jam, join the other cars in driving onto the dotted lines between lanes to create emergency lanes for first responders.