Hey Andreand!
In order to change the language for the Email address title, you’d want to change it within your list setting in your MailChimp account. Within MailChimp, you’d want to navigate to the lists page then click the gear icon, and in the pop up that appears click “Forms” the form can be translated under the “Translate it” tab on the page. Once the language is updated in the account you can update the plugin within the plugin settings.
hopefully that helps!