Error while trying to upload a picture.

Moving your site to another domain may require some changes to your config.

Try this at the beginning of wp-config.php, this makes your page independ from your host. Use http if have no ssl.

/* override the admin settings */
define('WP_SITEURL', 'https://' . $_SERVER['HTTP_HOST']);
define('WP_HOME', 'https://' . $_SERVER['HTTP_HOST']);

and you may require the plugin “make-paths-relative”

regards,
Thomas

@thomas66 I did as you required. The error is not showing anymore. However, I get the message as shown on the screenshot. I just finished a call with technical support of my hosting and they claim I need to delete some files to get it working properly, which I just did. It did not help. I just got “Missing a temporary folder” message. Appears as I if deleted it.

Any suggestions on what should I do next?

And thanks.

After following this tutorial:
https://www.wpbeginner.com/wp-tutorials/how-to-fix-missing-a-temporary-folder-error-in-wordpress/

I get this error when trying to edit the page:
Failed to load plugin url: https://prockstem.com/wp-content/plugins/embedit-pro/tinymce_editor_plugin_cf.php

you have to talk to your hosting, the php engine is not enabled for that path (maybe the change of domain or maybe the folder or maybe your wrong permissions).
I see with browser plain text file.