Each contact has a preferred language region (preferred local) e.g. en/de.
By default, Aivie does not save this, but you can use the forms to automatically fill in the user’s preferred language. j
Each form is language dependent, so you can assume that if someone fills out the German form, they speak German. So you can use a hidden field (preferred local) to automatically set the preferred language for each user.
If you use our package, this is already set up with you directly this best practice.