“Sending confirmation” false language in Safari browser

Hello,
if anyone subscribe to the newsletter with the mailjet widget in the Safari Browser the sending confirmation text is shown in german (default language). And also the double-opt-in E-Mail is sent in the default language.
The title of the form (widget) is shown correctly in english.

In other browsers like Chrome the text is shown in the right language and also the double-opt-in E-Mail.

Can you please help me to fix this?

Safari: https://ibb.co/7GtjHC1
Chrome: https://ibb.co/0G6LTT3

Best regards,
Armin