In addition to occupation, also nationality, religion, social roles (housewife, student), identity. https://www.realfastspanish.com/grammar/spanish-articles
Yes, Unfortunately, DL tends to use the indicative sentence structure for questions rather than the more standard inverted order that Spanish uses. In both English and Spanish, the indicative structure relies on rising intonation at the end of the sentence.
It asked me what one two three was, Image link https://docs.google.com/document/d/1DF3QnzokiT83CwIds3P2_y6miXaDzdNeml9BeH5pKwY/edit?usp=sharing
There are situations in which Spanish doesn't use "un" whereas English uses "a". See this: https://www.spanishdict.com/guide/using-the-indefinite-article-in-spanish
P.S. I encourage you to use good punctuation and spelling. Otherwise, I suspect you will be marked wrong many more times by DUO.
After 10 mistakes, I gave up counting. All the mistakes make you difficult to understand (hard to figure out).
Just a comment. It would be a little better when one is required to start a sentence with Él that you actually have it in the little keyboard. DL spends so much time trying to get us to pay attention to the accents, but then one is forced to write the sentence ¿él es estudiante? starting without a capital letter. To make my point I had to go to Spanish text somewhere off-site and copy and paste the two letters. Not everybody has a Spanish Keyboard. It may be trivial, but appears fixable.
Duolingo ignores capitalization, so writing names of people or even "I" in lowercase will be accepted. Similarly, writing random stuff in capitals will also be accepted. Just be aware of it and look up capitalization rules for each language you learn, eg. in Spanish names of weekdays, months and even languages are written in lowercase, but if you write them in uppercase, it'll be accepted, so keep that in mind.