1. Stuck at 0%

Stuck at 0% is the error that your server can not download and unzip the demo content. In your server hosting, find a Select PHP Version > PHP Extension and select Zip to fix this error.

2. Warning Notice in FrontEnd

Warning Notice in FrontEnd occurs when you import the demo sites in the frontend. For example
To solve it, add the following code to the bottom of your wp-config file to fix it.
@ini_set('display_errors', 0);
@ini_set('display_startup_errors', 0);
define('WP_DEBUG', false);
define('WP_DEBUG_LOG', true);
define('SCRIPT_DEBUG', false);