Can mean a lot of things, but probably a camera flash here — which is the same in both English and French.

This is the most mysterious and most interesting line in the song, linguistically. According to my research (see especially here and here) "faire des langues" is an unusual expression in French that would confuse even a native speaker. It seems to be borrowed from Spanish, where "hacerse lenguas" (making tongues) means the equivalent of "praise to the skies" in English or "ne pas tarir d'éloges" in French, which is of course what we'd expect Serge to say.

I think in context, this line means three things at once:

1. "We're praising one another to the skies"
2. "We're making out" (Serge probably chose this weird Spanish expression because it got tongues/langues in there, to suggest French kissing)
3. "We're 'doing languages'" ("langue" means both tongue and language in French) — playing around with English and French, which is just what they're doing. And I'm doing. (Maybe I should have called this blog fairedeslangues.com?)

I chose "we're blowing smoke up one another's asses," both because it colloquial and a bit weird, and mildly sexual, like the original. But it doesn't get the whole language play thing going.

Another interesting one. "Pick-up" is obviously an English word that took on a life of its own in French.

In my Canadian English, it can only have one of two meanings:

1. A pickup truck, which can't be meant here
2. The things on electric guitars that pick up vibrations on strings and turn them into electrical signals capable of amplification — which it's hard to see as flying around in a car cash. But maybe.

In French (and UK English), the main meaning is apparently the tonearm (and possibly the cartridge/needle) of a turntable — another musical meaning. Very possibly they have a portable record player in the car, and the tonearm went flying off.

The other most likely meaning of "a pick up" is... someone you picked up, a partner in casual sex. Maybe the other person in the car has gone flying a bit here.