Go hiking! It's many Germans' favorite pastime and we have well-signposted hiking trails everywhere. In Grünwald you're quite close to the Bavarian alps and lakes, really beautiful areas.
Germans have quite a different way of communicating compared to Americans. Small talk with strangers is not as common. Don't take it as rudeness if the supermarket cashier doesn't really smile or ask about your day. People are quite direct. If you ask someone how they are, be prepared for an honest reply.
Germans have many dialects and Bavaria is known for having quite a heavy one. If you know some German, you might still have some problems understanding people in Bavaria.
Public transport is good, but not Japan- or Switzerland-good. When going on a trip, take possible delays into account. Don't rely on a 5 minute connection in Mannheim HBf.
An electronics repair kit, e.g. the ifixit toolkit.