Hello,
Unfortunately, since this is an HTML Template, you will need to change the Files individually and you will need to manually copy/paste the HTML Codes for the Headers/Footers to all the Templates.
However, this is Definitely Possible by having a Centralized File for the Menu and this can be achieved easily using PHP. Please use the following steps:
Change the .html Extension of your files to .php .
Create a File named header.php and add the Header Codes to it.
Then, include this file in the Header Area. Example:
[ch_pre type="php"]<?php include('header.php'); ?>[/ch_pre]
This will definitely work fine. Hope this Helps!
Let us know if we can help you with anything else or if you find any further issues.