After the import of your pages, if no custom menu is defined, by default WordPress will show all your site’s pages as menu items. Obviously, specially if your site has plenty of pages, this default approach may not work for you.
To remove this default WordPress menu and create your own is quite easy. You shall go to Appearance->Menus and add your own custom navigation menu.
Posted in: Content export / import Why do all pages appear as menu items after the import?