Unfortunately, those are the javascript that are needed and the mechanical manuals platform is open so it uses Open Source modules, there are no dedicated programmers.
The .js and .css are compressed and downloaded once a week so they do not influence the load time of the page nothing more than the first time and the first page you access.
Regarding the slowdown of your processor, indicate that the problem is exclusively yours, the JavaScript perform very basic functions that do not require intensive processor use so that the page does not slow down or even in an old mobile.
Verify that you do not have accessories or navigation bars in your browser that are generally those that usually cause such problems.
The page is normally charged between 3.5 and 4.2 seconds which is an achievement taking into account that we have more than 500,000 registered users and up to 350 simultaneous users.