404 error page, adjustments needed

What I’m coming here for is that all the links on this single page are 100% reason.
Sites that are recreated have indexing links that are no longer used, but depending on the URL they lose their CSS and JS settings.
So just for this page, the full address of all third-party links and resources would be very useful and relevant
I created a 404 page that loses all configuration when the link cannot correctly point to the site’s CSS and JS.
Errors occur when links are shortened, such as:
/assets/styles.css - should be: HTTPS://mysite.com/assets/CSS/styles.
The same for all other links, whether images, js, or any other

The same would be very useful for navigation links, full links are more efficient.

Example: a website that uses folders to organize pages, navigation bars or links are lost.

Another feature that would be extremely useful is creating unique navigation menus, headers and footers for every project.

In these last points I believe that nothing is impossible, it just takes dedication.

We can have a header, main content and footer builder, even several if necessary