Ya versus Za
I am getting a lot wrong because I do not know when to use ya or za. Please help
The word habari is an N-class noun meaning its singular (class 9) and plural (class 10) forms are the same.
The word for "of" is essentially just -a, a very common little word that has a stack of different forms because it takes a consonant prefix that agrees with (changes according to) the noun class of the word before it (the possessed object).
You can see a table with all of the forms here: https://en.wiktionary.org/wiki/a#Swahili
The other possessive words -angu (my), -ako (your, singular), -ake (her/his), -etu (our), -enu (yous guys's) and -ao (their) take the same consonant prefixes and these are very similar to the subject/object prefixes on verbs, making it relatively painless to learn, even though that table might look scary.
So, for an example of this, we can use the word nyumba (house(s)), which is in the N-class and thus doesn't show if it's plural or singular directly.
nyumba yangu = my house
nyumba zangu = my houses
nyumba ya watu = the house of the people
nyumba za watu = the houses of the people
Of course, it doesn't help that two of the common translations of habari happen to be uncountable in English, "news" and "information", but we can imagine that habari means "piece of news/information" in the singular and "pieces of..." in the plural.
In the greetings, they're more or less interchangeable, with z-, at least theoretically asking for more information than y-, but I think in some cases, one is simply more common than the other just because of convention. In my admittedly rather limited exposure to Swahili, it seems to me like habari za asubuhi and habari yako are more common than their equivalent forms with z- and y- swapped. If you're really interested, you could try googling these phrases in quotation marks to see which ones are more common, but both are grammatically correct in any case.
It doesn't have to do with tense, it has to do with the word. I'll give examples Kiti ni kichafu = The chair (Kiti) is dirty (ni kichafu) Maembe ni machafu = Mangoes (Maembe) are dirty (ni machafu)
It's confusing but you get used to it. I'm not a native speaker. I'm working on speaking like one someday but I've only been studying Swahili for about a month and a half.