When your site executes an operation Max Execution Time means the measure of the time (in seconds) it takes to execute the single operation.
The max_execution_time can be set by modifying multiple files. They are .htaccess, php.ini, .user.ini, or wp-config.php files. You are gonna need FTP access to modify those files. You can find the credentials for your FTP access from your hosting provider.
To set max_execution_time please follow the steps given below,
1.Go to your WordPress root installation folder and locate any of these files .htaccess, php.ini, .user.ini or wp-config.php
php_value max_execution_time 300
@ini_set('max_execution_time' , '300' );