Could not complete the backup because the script timed out. Try increasing your PHP max_execution_time setting.

You can Go to php.ini and set the memory_limit variable to some higher value like 256M or 512M

In case if you dont find php.ini file on the server.

You can find it here /usr/local/psa/admin/conf/  or in etc/php.ini file.

 Make the changes and dont forget to restart the server again.

To Restart the server you have to run following command  :  service httpd restart ​on your command line like putty.