How to add smoothness when opening a block in JS?

Question

css

Good day! On the page, the task is to open the block when clicking on the title, which is initially set to display: none, this has been successfully implemented. The block hides and opens.
I screwed js for this: https://rosautodor.tmweb.ru/wp-content/themes/beth...
The page I'm making up: https://rosautodor.tmweb.ru/filials/

Question, how to make a smooth opening? So far, I tried to register from the options through css transition, but this property does not work.