Hi @remo,
Welcome to the forum.
Are you looking to have the option to view the form in multiple languages?
if so, then that is unfortunately not possible. One of the features I would love to see in ActiveCampaign is the ability to add some conditional logic, which could possibly allow you to do this, but it would need a lot of custom fields, as each language field would need to be entered as a separate custom field.
If you are only looking to change the language of the form itself, then you can just type the custom field options in the relevant language and change the description on the form.
I hope that helps.