I found a workaround: the URLs of my dynamic pages were formed with the field “project name”. Since my homepage is in German, I suspect that special German characters in the project name caused the problem.
my workaround: I added a field called “number” and gave each film a number. Then I changed the URLs from “project name” to the “number” field.
You can do this here:
At this menu location shown in the image above, I first removed the field “project name” and added the “number field”. → save.
Concerning my 2 blue arrows in the image of my original post, the correct setting for the dynamic link is “next/previous dynamic page”.