Infinitive vs non-finite verbs ("ich esse nicht")
Duolingo accepts both "I do not eat" and "I am not eating" as translations for "ich esse nicht", but these translations could have different meanings: "I do not eat" could be interpreted as "I never eat anything", whereas "I am not eating" could not.
How can I tell which meaning is intended when hearing the German phrase? Could it be used to mean either?
There wouldn't be two meanings of "Ich esse nicht." in German because German doesn't have the present continuous tense ("I am verb+ing...). "I don't eat." is the same thing as "I'm not eating.": "Ich esse nicht." As elae said, you would say "Ich esse nie." to say you never eat.