static front page not working

I have 3 languages:

• Danish (The main language)
• English
• German

If I change the Static Front Page in English or German, it makes the other settings vanish – even the main (Danish).
It automatic makes the Index page the page the blog-page.

Can I change this manually in the code somewhere?
I am using the Avada theme

Danish page
English page
German page

https://wordpress.org/plugins/polylang/