Saving a Block To Library Issue

I have a question? I am starting a new site with a custom built header This includes a nave with drop down on hero image etc. When I add this to my blocs library to use on new pages it seems that evrything is saved except the menu. Then I have to build a new nav menu for each page individually with all the classes I have. Is there something I can do to get the menu to move as well? When I add the custom saved block it goes back to standard menu.