why not my lawyer is smart
"My lawyer is smart" would be:
"muHaamiyyaa dhakiyy(un)" (Formal Standard) | "muHaamiyya dhakiyy" (informal).
Should this not also accept 'smart lawyer'?
Yes, technically that's correct since indefiniteness is implied. As long as you dont say "the smart lawyer" it could be counted as correct. I think they just want to make sure you know it's indefinite.
In English, the "lawyer" word is a countable noun - which needs the article.
The lawyer, a lawyer
An amazing lawyer, a smart lawyer, the smart lawyer, and so on.
Why not a lawyer is smart?
"A lawyer is smart" would be:
The Arabic sentence for "A lawyer is smart" is the same with the English sentence's "The lawyer is smart". This is one of the evidences which shows ال is not the same as "the" in English.
Why do they keep insisting on nonsensical sentences like "the generous door" and now this one?
Does the n here sound like 'th' to anyone else? It is consistently sounding incorrect for me
There is no n in this phrase. It's ذ, not ن. You can tell the difference as the first one doesn't connect to the following letter (ذكي), while the other one does (نكي).