Turnstile officially supports English only. You cannot change the language of Turnstile itself, or of the labels and field names Turnstile adds to quotes, invoices, emails, and customer-facing pages.
What stays in English
Labels and field names that Turnstile generates are always in English. Examples are Subtotal, Total, billing frequencies like Monthly, signature block labels, and invoice headings like Amount due.
What you can write in any language
You can type any text-based field in the language you choose, including:
Text blocks and terms on a quote or quote template
Product and service descriptions on a quote
PDF attachments added before or after a quote
Invoice memo, footer, and header fields
Invoice email and signature request email content
Can I create a quote in multiple languages?
Turnstile does not support quotes in multiple languages. As a workaround, you can type both languages into the text fields of your quote, like text blocks, terms, and product descriptions. To use both languages on every quote by default, add them to your quote template in Catalog > Quote templates.
Labels that Turnstile generates, like Subtotal and Total, always appear in English.
Can I invoice in multiple languages?
Turnstile supports English only. As a workaround, you can type both languages into the memo, footer, and header fields of your global invoice template in Settings > Default invoice settings. Both languages will then appear in those fields on every invoice.
Labels that Turnstile generates, like Amount due, always appear in English.