A lot of good advice here! One thing I would add is that large international flights typically board early. So your long-haul flight to Seoul may board 45 minutes or more in advance. And since you are in Business Class, you will board earlier than most.

My advice would be that once you arrive in Munich, check your phone (or look at the departure acreens) to find out what gate your Seoul flight is leaving from, then go there right away. No rush, but don’t hit the gift shop just yet. Once you get there, the screens at the gate should tell you when the boarding time is (or you can ask the gate staff.). Once you confirm that, you can leave for the restroom or to grab a quick snack.

You shouldn’t have to worry about a full meal because they normally feed you well in business class. (Free booze, also, if that is your thing.)