The “grey screen” you’re seeing is the Directory Listing. You should upload the files on the htdocs folder (the WP folders and files should go to the htdocs of your domain; I’ve seen the domain escolanovotempo.cf is added as an Addon Domain, so you need to upload the files on escolanovotempo.cf/htdocs/ ← HERE).
For digwebinterface.com it seems that the nameservers are a mix of both InfinityFree and Byet Internet Free Hosting nameservers.