How can I speed up my website?

The Accordion Menu's code is optimized, that is why it is loading from cache files, to only load the codes, that it needs, and it's also very small, so to track down, what is making your website slow, google "website speed test", and it will show you, what is loading for how long, and you will see, which part of your website, that you need to change. Usually the Time to First Byte is the problem, which is the amount of time until the first byte is received from the server, and that is the indication of the speed of your server.

Joomla

If this Time to First Byte is more than 30 sec, then probably there is a problem with some code, and you should go to the ExtensionsPlugin Manager → filter out the system type plugins, and disable them one-by-one to see, which one is causing it.