What Magix product or service are you really referring to? I trust it's not really magix.info. :-)
If you're referring to Website Maker, you'd have to delete (or at least hide) the page in question in the "Pages" panel on the left-hand side of the Website Maker editor. This will lead to the associated entry in the navigation bar being removed.
just some additional explanation: click on your navigation with CTRL-key, then go to the website maker panel on the left hand side, click on "characteristics" (I guess that's the word, as I am working with the German version), then on "navigation" again. Now, all your project pages are visible. Click on the "eye" of the page that you would like to delete from the navigation (colour turns from orange to grey). All pages with a grey eye are not shown in the main navigation. It is also possible to create a sub-navigation. If you are interested in that, there is an interesting workshop about building sub-navigations: http://www.magix.info/de/website-maker-how-to-build-sub-navigations.online-training.44907.html
If you have further questions, just ask !
regards,
Aussie-Elly