without access to phpinfo I can make regular recommendation that you up
http://php.net/manual/en/function.set-time-limit.php
you should be able to solve by setting your php run-time. Note: you will want to run a phpinfo to see if changes you make are actually reflected in phpinfo.
here is one of our free modules that will display phpinfo from you back office, i.e. if you make runtime change via .htaccess this will display correct php info. for root phpinfo it would not know about any changes to php that are made during PS execute.
https://www.prestaheroes.com/en-us/modules/prestashop-module-display-phpinfo-phpini