If you go to the wikipedia page at https://en.wikipedia.org/wiki/Swahili_language and go to section 5.3- Agreement. You can see how the -a preposition (of) changes depending on the noun class.
It's one of the more advanced things so if you get it wrong, native speakers will still understand what you're saying.
Or how is your evening. This is a greeting, isn't it. How's your morning/day/evening going = Good morning/day/evening.
The proper sense is missing from the dropdown glossary.