"Good morning grandmother?"
Translation:Habari za asubuhi bibi?
not at all (nothing in Swahili is gendered), the prefix of '-a' following a noun is completely dependent of that noun, and is governed by noun classes.
Usually for the noun class 'I/Zi', 'ya' is singular and 'za' is plural i.e.
ya mwalimu (a teacher's house) - nyumba
za walimu (teachers' houses)
In this case, 'habari ya' and 'habari za' are interchangeable since 'habari' is 'news' which technically isn't countable
The depth with which Duolingo covers noun classes is definitely lacking, and honestly even when I was formally learning the language as a kid, understanding noun classes was a pivotal point in my learning
It depends where. In Kenya, this is generally more common:
bibi = wife
nyanya = grandmother
Whereas in Tanzania, it's generally:
bibi = grandmother
mke = wife
nyanya = tomato
Just a generalisation though. Most people who speak Swahili speak it as a second language, and among native speakers, there are pretty diverse dialects.