Changing the default language tells Tringify that your original store content is now written in the selected language. The primary storefront also switches to that language.
This change does not translate or rewrite your existing original content. Translations previously stored for the new default language are removed, and the former default language remains enabled as an additional language. You must add translations for the former default language if you still want to publish it.
If the selected language is not enabled yet, it is added when your plan has room. Otherwise, remove another non-default language first.
Export any translations you may need later.
Make sure the original content is already written in the language you want to select.
Open Settings > Languages and choose Set as default beside that language.
Review every warning, then choose Change default to confirm.
Review the primary storefront and add translations for every additional language you still publish.