Nous nous voyons á peine
Hardly anybody is "très peu de monde" in French. We would as well use "presque personne" (almost nobody).
l'un et l'autre
It's common to say 'au revoir'.
Pretty solitary, I'd say. You hardly ever see 'em talking to each other.
Prenez soin l'un de l'autre
In French, trombone is also called "trombone." The word is pronounced similarly to the English term.
You don't. You only say Shabbat shalom in Hebrew. If you are asking how French Jews greet each other on Shabbat, they say "Shabbat Shalom"
se mettre à côté l'un et l'autre
Indeed they do. As the French would say, "Viva la difference"!
chaque appareil
pour chacun
chaque jour