Issue with Header

Hi,

I am trying to show my slider from the top of the page and that the main navigation menu it's transparent when I arrive and then it sticks when scrolling down with a white background.

The only issue it's that somehow my main navigation menu it's not transparent before scrolling right now.

Please check : https://www.thefrenchcandle.com/homepage-v7/

My custom css looks like
.site-header {
display: none;
}

/*to show logo on its real size*/
.main-navigation .navigation-logo img {
height: auto;
position: absolute;
left: 0;
}
.main-navigation:not(.navigation-stick) {
position: relative;
z-index: 99;
}

/* to remove the arrows and add 20px separation*/

.menu-item-has-children .dropdown-menu-toggle {
display: none;
}
.main-navigation .main-nav ul li.menu-item-has-children > a {
padding-right: 20px;
}

/* nav links effect */
.main-navigation .menu > .menu-item > a::after {
content: "";
position: absolute;
right: 0;
left: 50%;
bottom: 15px;
-webkit-transform: translateX(-50%);
transform: translateX(-50%);

display: block;
width: 0;
height: 1px;

background-color: currentColor;
transition: 0.3s width ease;
}
.main-navigation .menu > .menu-item.current-menu-item > a::after,
.main-navigation .menu > .menu-item > a:hover::after {
width: 50%;
}

Can you please help me ?
Thank you,
Jesus