In german, "Hallo! Guten morgan!" means "Hello! Good Morning!"
Hallo means Hello.
Guten means good.
Morgan means morning.
When we come across with a friend or someone I know, we would say "Hallo!" for informal greeting. If we come across a stranger, we would say "Guten Tag!" for formal greeting.
Tag means day. Therefore, Guten Tag means good day.
How about to say "See you tomorrow" in german? "Bis morgan". Morgan here means tomorrow. Yes, it is the same word for morning. "Bis morgan" literally means "Til tomorrow".
When we say goodbye, there is a formal way and informal way. "Auf Wiedersehen!" for formal way. "Tschüs!" for informal way. Of course, we can say "Bis später!" for "See you later!". ü sounds like 淤泥的淤 in putonghua. ä sounds like e. When say Tschüs! to whom understand putonghua, don't break it into 2 separated sounds; otherwise, it sounds like foul language - 去死。