What is triggering the language change after the page loads? That is where you will be able to also trigger element changes.
The code you have currently written will only be evaluate on page load (as you stated)
There is an example in the docs of using a click event to trigger a language change - if you are doing something like that you could also manipulate elements on this change as well.
https://www.wix.com/velo/reference/wix-window/multilingual/currentlanguage