Hello,
Thank you very much for choosing our theme and for contacting us.
Please make the full backup of the site and export the theme settings and follow this instruction: https://xtemos.com/docs/basel/installation-process-2/
If you still need help, please contact us, provide your site admin access and advise what demo you would like to upload, I will help.
Please note uploading the demo would reset the current settings but remain the content.
In order to enable out-of-stock/in stock, you need to enable the Manage stock option in the Woocommerce > Settings > Product > Inventory.
Best Regards