Why does css/js animation slow down?

Question

css

Hi all!
I'm making a calculator for a site in the form of a slider. I found the slider on the Internet and adjusted it for myself. Blocks are opened via js. So, having posted it on my site, I see that the slider animation slows down quite a lot on a weak laptop, although it works at 60 fps on phones and my work computer (sometimes you need to wait a couple of seconds to load either styles or js).
Tell me how you can optimize the project so that the brakes disappear everywhere?

Here is the code: https://codepen.io/pen/NWGeyrM (there are styles that will not be displayed in layouts, since these are styles wired into the site, but I think this is not a problem).
I'm completely new to layout, so please don't throw stones :)

Answer 1

You can include jquery, and there are a couple of lines of code. slideDown, slideUp