Alright, thanks Christian, I'm gonna check this.
It's good that you respond, I have another question regarding the Polylang plugin. I saw you're response here:
I tried your suggestions, but the result is still the same. I tried sticking to "The language is set by the directory name in the pretty permalinks". When using this option I can see all the pages in English in cornerstone, if I have switched the language to English, and when I switch to German I see all the German pages. However if i try to edit any of them I see the "iFrame response" error.
If I keep my settings to "The language is set by the content" I can't see any of my German pages with cornerstone, no matter which language I am using at the moment. And if I try to edit an English page that I see with cornerstone I get the same iFrame error again.
The website in question is https://body-wisdom.net/
Do you have any suggestions? What can I do to fix this?