Thanks, this helped a little. Dokuwiki started but, then there is a lot of errors like this:
Notice: Undefined property: dokuwiki\Cache\Cache::$page in /var/www/dokuwiki/inc/Debug/PropertyDeprecationHelper.php on line 74
Notice: Undefined property: dokuwiki\Cache\Cache::$file in /var/www/dokuwiki/inc/Debug/PropertyDeprecationHelper.php on line 74
Notice: Undefined property: dokuwiki\Cache\Cache::$mode in /var/www/dokuwiki/inc/Debug/PropertyDeprecationHelper.php on line 74