Hi There,
Thanks for writing in! It seems that your PHP memory limit is set to 256M which should be alright, but sometimes it requires more memory allocation.
Could you please try increasing your PHP Memory limit by editing your wp-config.php file which can be located under the root of your WordPress installation.
Add the following lines into that file.
define( 'WP_MEMORY_LIMIT', '512M' );
define( 'WP_MAX_MEMORY_LIMIT', '512M' );
You can add it before the line
/*That's all, stop editing! Happy Blogging. */
Also I see that your PHP max script execution time ( PHP Maximale Skript-Ausführungszeit) is set to 30, could you please try increasing it to 120 or a higher value and try editing your page again to see if that resolves your issue.
Make sure to purge your server cache before testing.
Thanks!