Add fade effect on magnifying glass (search icon)

Hi guys,

As you can see on my website in private content, I added some code to make search icon fade out when opening burger menu:

@media only screen and (max-width: 989px) {
.html_av-overlay-side.av-burger-overlay-active #top #wrap_all #header .menu-item-search-dropdown a {
  visibility: hidden;
  opacity: 0;
  transition: visibility 0s 0.5s, opacity 0.5s linear;}
}

My question is: which code do I need to add to make it fade in when burger menu is closed?
I would like to add this code to achieve this:

.visible {
  visibility: visible;
  opacity: 1;
  transition: opacity 0.5s linear;
}

…but I don’t know which class or ID to add before it.

If needed, you can find a link and credentials to my website in private content.
Thanks a lot!