thanks a lot. It works, however, this page was only my testing workplace without google indexing. Now I have set the main installation on the page http://napocatku.cz/ You can see that the texts here are extracted directly from the pages, not excerpts which I added according to the wordpress documentation at https://codex.wordpress.org/Excerpt (in function.php of my childtheme)
Can you please tell me which settings is missing? I can send you login details if you need.