Translations:Adjust your terminology/language/3/en
From SimplyBook.me
Changing language/wording for the whole system (without notifications templates)
Settings -> Custom wording & translations also allows you to adjust the language of the whole system. Please select All system translations tab to change all system wording.
Please note! It is not possible to have fully separate languages for admin and client sides as some of the texts are used for both sides. So you may have client side fully translated to one language and have admin side in a different one, but with some words form the client side language.

The system as well allows to download .po file, translate it with PoEditor software, upload the texts and apply to your system.
