I have seen in progressive tense sometimes नहीं is before the verb and sometimes after. Which option sounds better?
The usual order is नहीं followed by the verb. You switch the order when you want to place emphasis on the negation.
The duolingo is doing wrong
The Word नही comes after the verb and sometime after which is correct
Both are correct. Before the verb is the usual placement. After the verb emphasises the negation.
In the simple present we learned that the auxiliary form of होना is optional. In every example in this lesson with the progressive present, होना is present. Is it not optional in the progressive tense?
It is optional for all present tense negative sentences. The version without the है should be accepted for this sentence. You can report if it's not.
Thanks, vinay92! I didn't try it. I was just wondering, since I hadn't seen any without it.