Are you free tonight?
So oddly, I answered “Abend” with “Nacht” which made sense to me as the translation is for “night”. But, it replaced my answer with “Abend” and then counted it as correct. Does it just consider them equivalent or is the correct expression “Abend” and not “Nacht”?
Literally, you are right.
However, the use of these expressions is different in the two languages.
“Are you free tonight?” in English would be okay for e.g. in invitation for dinner.
No one in Germany would ask “Haben Sie heute Nacht Zeit?” for dinner. That yould only be appropriate for e.g. a hunting trip until the early morning .
So, for the overwhelming majority of occasions the translation with “Abend” is correct.