Use the language picker in the menu (and again in the footer). Choose English, Español, Français, Deutsch, Português, or 日本語. That changes navigation, search, sign-in, join, home, directory, swaps, forum chrome, profile tabs, classroom hub titles, help/FAQ/about titles. Your choice is saved in a cookie for about a year; until then we follow your browser language if we support it.
Forum posts, member bios, house rules, legal pages, and help articles stay in the language they were written — usually English. That is on purpose so rules and member words are not machine-translated. We will not auto-translate the house rules. Languages I write in on your profile is separate: it tells penpals what language you write notes in, not which site menus you see.