Updating/Publishing failed

If I want to publish or update a post with Gutenberg, I get an error. I also can’t preview the post.
Error log:

2018-12-04 20:49:44	Error	404	GET /wp/index.php/wp-json/wp/v2/users/?who=authors&per_page=100&_locale=user HTTP/1.0	https://test.silas229.de/wp/wp-admin/post.php?post=2&action=edit
2018-12-04 20:49:44	Error	404	GET /wp/index.php/wp-json/wp/v2/users/?who=authors&per_page=100&_locale=user HTTP/1.0	https://test.silas229.de/wp/wp-admin/post.php?post=2&action=edit
2018-12-04 20:49:44	Error	404	GET /wp/index.php/wp-json/wp/v2/taxonomies?context=edit&_locale=user HTTP/1.0	https://test.silas229.de/wp/wp-admin/post.php?post=2&action=edit
2018-12-04 20:49:44	Error	404	GET /wp/index.php/wp-json/wp/v2/taxonomies?context=edit&_locale=user HTTP/1.0	https://test.silas229.de/wp/wp-admin/post.php?post=2&action=edit
2018-12-04 20:49:53	Error	404	POST /wp/index.php/wp-json/wp/v2/pages/2?_locale=user HTTP/1.0	https://test.silas229.de/wp/wp-admin/post.php?post=2&action=edit
2018-12-04 20:49:53	Error	404	POST /wp/index.php/wp-json/wp/v2/pages/2?_locale=user HTTP/1.0	https://test.silas229.de/wp/wp-admin/post.php?post=2&action=edit
2018-12-04 20:50:03	Error	404	POST /wp/index.php/wp-json/wp/v2/pages/2/autosaves?_locale=user HTTP/1.0	https://test.silas229.de/wp/wp-admin/post.php?post=2&action=edit
2018-12-04 20:50:03	Error	404	POST /wp/index.php/wp-json/wp/v2/pages/2/autosaves?_locale=user HTTP/1.0	https://test.silas229.de/wp/wp-admin/post.php?post=2&action=edit
2018-12-04 20:50:14	Error	404	POST /wp/index.php/wp-json/wp/v2/pages/2/autosaves?_locale=user HTTP/1.0	https://test.silas229.de/wp/wp-admin/post.php?post=2&action=edit
2018-12-04 20:50:14	Error	404	POST /wp/index.php/wp-json/wp/v2/pages/2/autosaves?_locale=user HTTP/1.0	https://test.silas229.de/wp/wp-admin/post.php?post=2&action=edit