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
2. Select any of the files above and Edit and paste these directive code given below,
3. Save the file.

Directive code

for .htaccess

php_value max_execution_time 300

for php.ini or .user.ini max_execution_time=300 for wp-config.php @ini_set('max_execution_time' , '300' ); The recommended time is '300' minimum.