This is an area that is culturally different
from the US, in that people do greet one another in German-speaking
countries. It is common to enter any business, any building,
any "arena" - and greet (be greeted by) folks
around you, whether you know them or not!
Because of the understood relationships
of "Du" and "Sie" (which you will learn
later) - it is easier for people to have a conversation
without feeling estranged or like they need to tread on
eggshells. As with anything, there are exceptions to every
rule, so don't be offended if you run into someone who just
doesn't want to talk to you!
Otherwise, --- greet everyone!