Translation:I have to buy
"Ninunue" actually means "buy me" in Swahili speaking countries. If you want to say I have to buy in Swahili it is "Ninastahili kununua"
It often confuses me when someone says "this isn't the way something is used in Swahili speaking countries", given that two out of three of the main course creators are not just natives, but teachers of the language outside this course.
I'll take your word for it about ninunue. It's just strange.