So, your theme isn’t the best if it’s hardcoding pagenames…
But, if you’re going to use that theme and not edit it, you’ll definitely need to change your Permalinks to a non-default setting to get “pretty” page names.
Then, you’ll need to create pages to match those links. Make sure the page’s slug matches the names you see in those URLS above (mosaic, about, contact for instance).
Or get a theme that was designed to actually work with WordPress.
Or edit your theme to use wp_list_pages() which will dynamically build up a list of pages to match what you have, not what your theme author thought you should have.