Hello @2b555,

You have to ask the hosting provider support to increase the max execution time from the PHP settings from the CPanel.

If the issue remains, deactivate the plugins not related to the theme and import the demo and check the issue. If the issue still persists, share the WP admin login details and Cpanel login details of your site so I will check and import the demo on your site? Also, please tell me which demo you want to import on the site?

Best Regards.