It's an irregular noun.

ma (with the umlaut) nner is the plural form of "man" in german not norwegian

I see where you're coming from but this sentence does not introduce subordinate clauses or something that could be classified as advanced syntax building. It even follows the same word order so it shouldn't be burdensome to translate.

Remember that ikke (not) usually follows the verb in order to negate it but in this example it precedes the noun. Some other instances where this happens are:

Han er en gutt, ikke en jente. - He is a boy, not a girl.

Det er en katt, ikke en hund. - That is a cat, not a dog.

"They" translates to "de" in Norwegian, and is not synonymous with the plural "you".

Since the English sentence is ambiguous, both the singular ("du") and plural ("dere") version is accepted in Norwegian.

Since it uses plural nouns, it doesn't need "you all" for "you" to be interpreted as plural.

"De" (always capitalised) is a now obsolete "høflighetsform" for the singular you. We neither teach nor accept it, as it's no longer in regular use.

You might encounter the formal second person singular/plural "De", object form "Dem" (note it is always written with a capital letter) if you watch films and tv from the early eighties or older, or set in older times, or spoken by older people. I still learnt how to use it in school, and it was still considered standard in business correspondence well into the Nineties.

While not current Norwegian, it is useful to know about.

You in English is ambiguous. It can mean both you singular and you plural. But together with a plural noun, it is plural. In Norwegian, we differentiate second person pronouns between singular "du" and plural "dere". Since it says "women", plural, in Norwegian "kvinner", also plural, the pronoun therefore has to be plural "dere". Compare: Du er kvinne, ikke mann. (singular - "entall" in Norwegian) Dere er kvinner, ikke menn. (plural - "flertall" in Norwegian)

Du is singular, dere is plural. I have noticed in more than one language course forum, that most confusions people have stem from the peculiarities, oddities and inconsistencies of English. In the case of Norwegian, the verb cannot tell you whether it is singular or plural, but the adjective or - in this case the noun after «er» -sometimes can, and so the difference is retained, as indeed it is in most languages.

"Du" is the singular "you", so it doesn't go with the plural "woman" and "men"

"Dere er kvinner..." but "Du er (en) kvinne...".