A handful of phrases will carry you through your first day in Berlin:

German	English	When
Hallo!	Hello! / Hi!	Any time, with almost anyone
Guten Morgen!	Good morning!	Until about 10 or 11 a.m.
Guten Tag!	Hello! / Good afternoon!	The standard daytime greeting in shops and offices
Guten Abend!	Good evening!	From about 6 p.m.
Wie geht's?	How are you?	Among friends
Gut, danke!	Fine, thanks!	The usual answer
Und du?	And you?	To pass the question back

To say who you are, use Ich bin… — Ich bin Marina. (I'm Marina.)