Page not found when published

I’m trying to build my website but I can only view pages I created when they are still in Draft. Once I publish them I get “page not found”. Secondly, if I create the pages with different names i.e. About, or Services and I then view the pages (in Draft format), the menu doesn’t update – it just shows “Home”. I’ve recently changed my theme to Blackbird, using a tutorial I found on Youtube. When the person in the tutorial creates new pages everything works as smooth as butter, but not when I try to do it :(. Please help.