There seems to be a bug setting the data type of links in a textelement within the gridder to "project" even if a page was linked. this leads to an error 404 of the wp-json API. I can change this manually everytime I add a link, but it is really annoying when linking lots of stuff ...
See the error on this page: www.relaunch.ameliemareiloellmann.de (click on "Impressum" in the footer)
I have set the permalinks as requested (pretty permalinks). I have reinstalled the theme and Wordpress 3 Times, always the same problem. When calling http://relaunch.ameliemareiloellmann.de/wp-json/wp/v2/posts/6 directly, you can see the error 404.
I also checked the database, the Post with the ID 6 ist the according page. Also I checked the .htaccess, the rewrite rules should be working.
Maybe a clue: When opening the page using the navigation, the link contains the data type "page", when linking the page in a text, the data type is "project" (you can see that on the page as well in the source code)