When my colleagues or friends greet me by asking "Alles gut?". I am only able to reply "gut, danke". What are different ways to reply in case you are in good mood or bad mood?
In Germany a common greeting is "Wie geht's?" It can be quite superficial or a begin of long conversation if your partner is really interested in. It heavily depends on context. "Alles gut?" can be used in the same way however it also can be meant to express a deeper interest into the persons problems, see below.
To both you might answer superficial in descending order of your mood: "Super, danke.", "Alles in Ordnung.", "Gut, danke.", "Danke gut", "Geht so.", "Nicht so gut.", "Beschissen." Further you should add to all: "Und dir/ihnen?"
"Alles gut?" might be used to show a deeper interest as a second question if the first response was not so good. I might have answered "Gut, danke." which is quite neutral. But my partner does not trust me or has noticed there is some trouble in my mind. Then he emphasizes his interest. Similiar: "Ist wirklich alles gut?"