Does 'Jouzu desu' mean you're very good in Japanese?

'Jouzu desu' means "is skilled." Said in response to something that you have done (spoken in Japanese, made a goal, knitted a sweater, cooked delicious food), it can be translated as "You're very good/talented [at that]."

In short, 'jouzu desu' is said when one wants to praise the skills of another.