Germany is a federal country, and a sensible first visit is two or three states rather than a lap of every famous name. Berlin, Munich, Hamburg and Cologne are the magnets. The Rhine, Bavaria, Saxony and the North Sea are different holidays. German is the language of tickets, bakers and announcements. English is widely spoken in cities and among younger people; it is not guaranteed at a regional ticket machine if you have already switched it to German by mistake.
Deutsche Bahn long-distance trains (ICE, IC) connect the cities. Regional trains and S-Bahn systems fill the rest. Delays happen often enough that a tight connection is a gamble, not a plan. The Deutschland-Ticket covers local and regional transit for residents and visitors who want that pass; long-distance ICE is separate. Cities are walked and trammed. Sunday still shuts most shops.
Cash has retreated but not vanished; some smaller bakeries and bars still prefer it. Cards and contactless are normal in stations and chain restaurants. Tipping is rounding up, not an American percentage. In summer the south is beer gardens and the Alps; the north is water and wind. Choose a cluster. Munich plus the mountains is one week. Berlin plus Dresden or Hamburg is another.
