A survey doesn't choose its own languages — it inherits exactly the locales configured on its domain. Add or change a domain's locales from Domains; every survey attached to that domain then needs its text filled in for each one.
Every piece of text a survey shows — field labels, answer options, and the survey's own copy (titles, button text, thank-you message) — needs a value for every locale the domain supports. This is enforced at publish time: a survey can't go live while any locale is missing a translation anywhere in it.