Cannot Re-size Remove Highlight Line Under Main-menu/Sub-menu

Hello

I’m trying to do something about that highlight line under the main-menu items; particularly under the second menu item, “Προϊόντα” with the drop-down menu. I managed to remove the line from all the menu items except for the second one using this:

.avia-menu-fx {
display: none !important;
opacity: 0;
}

I tried this as well but nothing:

#top .main_menu .menu > li > a { width: auto; }
.header_color .main_menu ul:first-child >li > ul, #top .header_color .avia_mega_div > .sub-menu {
border-top-color: transparent;
}

I would not mind keeping the highlight line if its width under the 2nd menu item can be fixed.
Please tell me how I can fix or remove that highlight line under the 2nd menu item.
I also wouldn’t mind having the highlight bar be on top of the selected category if that’s possible.

I used this css to widen the sub-menu for the 2nd menu item:

#top .main_menu .menu li ul a {
width: 251px;
}

Could this be to blame?