Reply To: Transfer the Agama pro to another site.
It looks that you have a problem with the Polylang plugin.
You should go to your server where the site is hosted, and delete the problematic plugin folder, located in wp-content / plugins /
You will need an FTP host, user & pass details from your server. Then your website should work.
I see that they have made a lot of changes, so it is possible that something made a problem
First, try to reinstall the plugin and if the problem persists, try to revert the plugin to previous version https://wordpress.org/plugins/polylang/advanced/
PS. I tested the newest version and found no problem in work with the theme.