As per your trailing message, i did ask the host company and their reply is :
Dear Client, This is not a server issue, the error message clearly tells “Call to a member function getStream() on a non-object in /home/girachin/public_html/wp-content/plugins/revslider/includes/slider.class.php on line 924” There is a mistake in the function call syntax, please check.
All permissions are fine. Kind Regards
They say, they have checked everything and everything is fine. Just the slider is the problem rest all is sorted out.