Translation:I am not a man.
I believe 男性 (だんせい) is generally used for male or masculine gender, and 男 (おとこ) is used for man.
Yes, you are correct. I found it is odd that Duo says it is correct to say 'I am a female' in the different lesson but incorrect to say 'I am not a male' here. But yes, both a male and a man should be accepted.
It's just what is used for connecting nouns, or な adjectives to the negetive of ある、which is ありません. ~ではあいません is most polite. Then there are ~ではない and ~じゃない. which mean exactly the same thing, just are less formal.
"I am not male" is literally correct here, not sure why it isn't accepted.
In another context, could this be translated as "there are no men"? If not, why?
I think that would be (男が) いません. [X is/isn't Y] and [there is/isn't X] are different sentences, it's a peculiarity of English that they use the same verb.
This answer was rejected when Duolingo asked me to translate "I am not a man."
I used boy and It is incorrect. I think man is otoko no hito. Is that right?
"otoko" on its own means "male". To mean "boy" you would want "otoko no ko", lit. "child-of-maleness".
'I'm not a man' is rejected and it doesn't let me report it ('my solution is correct' isn't among the options).
This app has too many grammatical errors. For example, this sentence has no subject and arimasen should not be used. You need to have native speakers vett this app.
Watashi is the subject, and arimasen isn't used. Dewa arimasen is just the negative form of desu, and it's perfectly fine to use with people. It just means "is/am not".
The subject is implied here. Without more context, we don't know what it is. It could be "I", "he", "she", "they", etc.
And ではありません is the formal negative of です.