burger menu not full screen and on the right side

.av-burger-overlay {
    box-shadow: -2px 0 10px #bbb;
    max-width: 400px;
    left: inherit;
    right: 0 !important;
}

see here: http://webers-testseite.de/elegant/

works ok and looks nice with a little shadow
by the way
if Ismael could help me again.
Is it possible to darken the background than ?
I inserted allready the div like here : https://kriesi.at/support/topic/mega-menu-effect/

but i do not see how i can influence the container. There is a class added to html (av-burger-overlay-active) but is this the way ?
Thanks