Dear @nypaloto, dear @Richard-Keith,
as the english site worked perfectly with the solution above, I wanted to start with the french and spanish versions of the site.
So I added another language in Polylang, added the page ID in the Polylang’s string section »frontpage_select_page« ...
... but on the front-page, when I click on »FR«, this link is still linked to the »EN« version of the site –> www.matteroffact.de
Does anyone has an idea, why this is not working? Thanks again for your help!
Greetings from Cologne