Capital: Berlin – which is not similar to the rest of the country but a stunning city none the less.
Transport: the Deutsche Bahn is efficient and fast and its extensive railway is a great way to get around the city. If you are on a tight schedule and trip, try the German Eurail pass. There are also plenty of buses!
Currency: Euros, cards are widely accepted across most places. But have some cash for flea markets.
Sim Card: Many sim cards are valid for entire Europe
Handy apps: Omio for booking trains and buses
Language: German, but most people speak a good level of English. Hallo = Hello, Dan-ka schon = thank you.