Hello I have a problem with slideshow (full width) - cant put new item and new picture

Error: Failed opening required '/home/platne/serwer69848/public_html/onepage/libraries/joomla/document/html/renderer/head.php' (include_path='/home/platne/serwer69848/public_html/onepage/plugins/system/shlib/shl_packages//ZendFramework-1.11.7-minimal/library:.:/usr/local/php81-fpm/lib/php'): Object of class stdClass could not be converted to string

thanks for help

http://www.e-psycholog.org/ Joomla 3.10