hack joomla backend not working

namespace Joomla\CMS\Toolbar\Button line 9 error

replace /home/thegoodw/public_html/[ redacted ]/libraries/src/Toolbar/ToolbarButton.php on line 9. 
 with a working file

themify footer on mobile centered

https://themify.me/forum/topic/centering-footer-widgets-on-mobile