Active page bold – not parent or sub page

well – be more specific in your selectors – change your rule to :

.header_color .main_menu ul:first-child > li.current-menu-item > a > .avia-menu-text {
  font-weight:700
}

the greater than (>) indicates that only the direct descendants are meant, and not grandchildren etc.

or you can do that by enfold – under advanced styling there is the choice to style only “main menu links” and that means only first level items.

i thought you like to have the first level only in that style.

ok – get rid of the bold setting for parent theme
( via : #top #header .av-main-nav > li.current-menu-item > a )
and use:

.header_color .main_menu ul  li.current_page_item > a > .avia-menu-text {
  font-weight:700;
  color: #000;
}