Your first word is (not jambo, you all know that one already), but:
The literal translation for this word is: News
But in practical terms it can mean:
How are you?, as in: What is your news?
So there you are, the next person that shouts “Jambo” you answer: “Habari” like a pro.
Now you will probably be showered in the latest News hot from the press, all gibberish to you, but A good reason to stick with your… Swahili Teacher !!