To increase the PHP Maximum Execution Time do the following:
Method 1: Editing .htaccess File Manually
Step 1: Locate the .htaccess file inside the root of your WordPress installation (located in the same folder as your /wp-content/ and /wp-admin/ directories) using an FTP client or file manager in your web hosting control panel (if you can’t find it see why you can’t find the .htaccess file and how to find it or if you’re not sure how to do this, ignore the steps below and contact your web host who can do this for you).
Step 2: Paste this code in your .htaccess file:
php_value max_execution_time 180
Step 3: Now save the file.
Note: If you still get the error, try increasing the value to 600.
Method 2: Using A Plugin
Step 1: If you're not able to edit .htaccess file manually, then you can install and activate the WP Maximum Execution Time Exceeded plugin. That’s all. The plugin works out of the box and increases the maximum execution time to 300 seconds.