Translation Jumbotron Front Page Section with Polylang

I have trouble translating the three word title and description on the frontpage of our website:
The most useful article I found is this here:
But the described solution doesn’t work for me. The string shows up in the translation section after modifying the functions.php but it has no effect on the site. I believe because I changed the content of the three word title and description in the customizer and I’m not able to load the demo content again.
Any ideas on how to proceed?
Thank you very much for your support!