Can I force one language for everyone?

Set the same language on all guests (select all, then change language). Guests can still switch the language on the RSVP page themselves.

Why does my German guest get an English email?

Their guest language is English, probably because they registered from an English browser. Change it on the guest row and resend.

Do I have to translate my texts myself?

Yes, for now. The standard texts exist in all seven languages, so untranslated templates still work; your custom sentences appear only in the languages you filled in.

How do time zones and languages work for my event and my guests?

Short answer

The event has one time zone, set under Edit Event, so calendar files and reminders fire at the right local time. Guest pages and emails come in the guest's own language: each guest has a language, guessed from their browser or set by you, out of English, Dutch, German, French, Spanish, Italian and Portuguese. You edit texts per language.

Time zone

Set it once per event; the picker suggests your browser's zone. Amsterdam events use Europe/Amsterdam, a New York event uses America/New_York.
The calendar file guests receive (Google, Apple, Outlook) carries the zone, so a guest abroad sees the correct local time in their calendar.
Automations such as the event reminder use the event's zone to decide when "7 days before" is.

Languages

Event language: the default for guests without their own language, set under Edit Event.
Guest language: shown as a small code on the guest row. It follows the browser language when a guest registers, and you can change it per guest or set it in an import.
Templates per language: in the RSVP editor and in every email template you switch languages with the flag buttons. A language you leave empty falls back to the standard text.

Mixed audiences

An international conference sends the same invitation in seven languages without extra work: each guest gets their language automatically. Write your own text in the languages you care about and let the standard text cover the rest.

Questions about this

Can I force one language for everyone?: Set the same language on all guests (select all, then change language). Guests can still switch the language on the RSVP page themselves.
Why does my German guest get an English email?: Their guest language is English, probably because they registered from an English browser. Change it on the guest row and resend.
Do I have to translate my texts myself?: Yes, for now. The standard texts exist in all seven languages, so untranslated templates still work; your custom sentences appear only in the languages you filled in.