By this, I am not referring to the autofilling of usernames and passwords - that is a supported feature. So it is expected that you will see the option to autofill a username or password using Kee Vault.
I suspect that Google is automatically translating some parts of their interface (such as the request to send the credentials to Kee Vault for saving) into your device’s language, which I assume is French. However, Kee Vault 2 itself is not available in any language other than English.
If you try to save some new credentials to your Kee Vault using this feature and it does not work, please provide some more information about how we could reproduce the problem since it is expected to work, although a lot is out of our control so it definitely can’t work for every single app or website.