You can edit this page with the Customizer. Simply go to your admin panel and navigate to Dashboard > Appearance > Customize > Appearance > Login. You will find several options give you the opportunity to customize your login page and you will be able to modify its layout, background color or background image.
To make your site completely private (intranet or full private content platform), you have to install and activate the My Private Site plugin. After that go to the plugin setting page (Settings > Private Site) and adjust options according to your needs. Here is a link of a well-written article about this subject : https://www.wpbeginner.com/beginners-guide/how-to-make-your-wordpress-blog-completely-private/ […]