Bien, merci!

Let me see, so usually the pattern of a "familiar" greeting would go:
"Bonjour, ca va?"
"Ca va bien, merci, et toi?"
"bien, merci."

Yes yes yes, classically that would be translated into the infamous:
"Good morning, how are you?"
"Fine, thank you, and you?"
"Fine, thank you."

Well, at least that's what they taught me.

Well here, in Senegal, the greeting has 4 basic lines (sometimes more, but inserted in Wollof; the country's social language; but because I know very little of, let's put it aside this time):
"Bonjour, ca va?"
"Ca va." And here's the catch, they prolong by asking:
"Ca va bien?"
"Bien, merci."

Note that the person who greets first is not being asked how he/she is doing. It's not important, because here, we assume that because they ask, they're well enough to bother with you ^^; )
Anyhow, back to the 4 basic lines of greeting. That, my friend, can be awkwardly confusing. Let's take an example where a grand director happens to find a small -oh-totally-lost-and-humble- asian trainee (note: I'm in Africa, so that kinda makes me.. ehm.. stand out?) walking up and down the corridor. The conversation starts with something like this:

"Bonjour, vous commencez aujourd'hui? Bien, bien.. ca va? Tout se passe bien?"
"Oui... ca va, merci. Et vous Madame, vous allez bien?"
... and there, I thought the greeting was over with a "oui" or a "bien, merci." But she continued...
"Ca va BIEN?" worse yet, in a tone of disbelief.
*Mia's lost, and with a tone degraded confidence manages to mumble*
"Oui, uhm.. oui, je vais.. uhm.. bien? uhm merci."

The same thing happened when I went to the trainees' cafeteria (if you could even call it so...), I greeted the guy at the entrance with a simple bonjour and he goes:
"Bonjour, ca va?"
Ok, so I have to answer, and to keep it short, I went:
"Oui, merci." The guy was approached by his colleague, and to put this occasion to use and cut short the greeting, I turned right, targeting food.

I was already quite far from him, when he shouted:
"Ca va BIEN?"

Yup, it was me he was addressing to.

And when I finally got that it was albeit something Senegalese do (and therefore considered impolite not to finish the 4 lines of greeting). So, I shouted back:
"BIEN MERCI!"