In Descriptions 3/2: my translation 'An American- Arab, smart girl' was counted as wrong. Is there a rule in this word order?
It has to do with the order of adjectives which is common in English, and which is common in Arabic. In Arabic, the adjectives that are about the identity come first (after the noun) and then quality adjectives (like "smart") come after.
In English, it is commonly like the example above; The quality adjective (smart) comes first then followed by personal or identity adjectives that describe the person or the thing.