We do not would be "noi non facciamo." "Faccio" means do (P.S. not sure if it's spelled with one or two Cs)
Probably because part of translating is expressing the concept in the correct way in the language you are translating to... (even if you have to adjust the word order to do so)
Us no - doesn't make sense in English.
Not us - is what English speakers would say.
These phrases are too unwieldy. They can be correctly interpreted and written in various ways, but only a few answers are "correct"
That's because only the interpretations that Duolingo marks as correct are a valid translation. Any other interpretations that you may be able to see (or write) for this phrase are wrong.
Languages are not a simple matter of this word here always equals that word there. If it were, we would already have babelfish-style translating machines that could instantly understand another language perfectly for you. Part of learning a new language is learning how to correctly interpret each phrase, including what things are idiomatic and what things can be deduced by knowing some basic grammar rules.
"Not we" what does that mean?
but "We, no" makes a bit of sense.
"Not we" is not correct English, you can't use the pronoun "we" after the word "not". Duolingo is wrong in this case.