This article explains how to create an estimate in a foreign language in FreeAgent.
Before you create the estimate, make sure that the language is set for the contact to whom you're going to send the estimate. This option is under 'Invoicing Options' for the contact.
You can choose the currency for the estimate as you create that estimate, but the language needs to be set at contact level.
Then when you create the estimate, it will be in your chosen language.
Please note that FreeAgent doesn't translate the description you type in, so if you want the description to be in the foreign language, you'll need to type it in in that language.
The estimate is then ready for sending as usual.