Lot of errors in back office 1.7 since upgrading in PHP 7

[crams]

Hi every body,
i got a lot of troubles in my back office  / prestashop  1.7.3.1/  since my hosting company upgrade to PHP 7.0.30, and a lot of modules and fonctions are not working correctly anymore.
here is a typical error message :
Notice: SessionHandler::gc(): ps_files_cleanup_dir: opendir(/var/cpanel/php/sessions/ea-php70) failed: Permission denied (13) in /home/afriksho/public_html/presta17/app/cache/prod/classes.php on line 439

Warning: Cannot modify header information - headers already sent by (output started at /home/afriksho/public_html/presta17/app/cache/prod/classes.php:439) in /home/afriksho/public_html/presta17/classes/controller/AdminController.php on line 1853

My hosting company did'nt help me to much, speaking about permissions, but did'nt find any issues.
I posted in french forum without success ... and so try to get help on english forum.

Any help would be apprecied.
 

Edited July 2, 2018 by crams (see edit history)