marco17 Kindly try to update your php version to Current Stable PHP 7.2.6 version or you can ask your hosting provider to update the same as the current version being used on your site is obselete henceforth, notification is appearing in admin backend :
Error
We have detected that your server is using PHP 5.3.29 which is obsolete and no longer receives official security updates by its developers. The Joomla! Project recommends upgrading your site to PHP 5.6 or later which will receive security updates at least until 2018-12-31. Please ask your host to make PHP 5.6 or a later version the default version for your site. If your host is already PHP 5.6 ready please enable PHP 5.6 on your site's root and 'administrator' directories – typically you can do this yourself through a tool in your hosting control panel, but it's best to ask your host if you are unsure.
Due to aforesaid reasons, I am unable to install the extension too as referred above as the installer is returning with blank page due to which unable to proceed with further steps of loading the syntax thereon