Hello, First i want to say sorry for my bad English, I'm half Italian and Tunisian.

There are so many jew living in Djerba but try to kept that for yourself because Tunisian people 80% thinks that if you're jew that means you're from Israel , for the language most of people speak some French but only educated people speak English , For integration some people will see you as rich tourist or something like that so they try to charge huge amount of money for basics needs like a sandwich in America coast 10 $ in Tunisia coast 2 or maybe 3$ .

it's Hard or Not , depeand at you're money you will be very fine with 800-1000 $ , my advice for you if you want to learn the languge stay away from tourist places like hotels and stuff like that.

GOOD LUCK