yes this was made due to the background transparency of the header on scrolling – but if you use a full color than it is obsolete!
on white case there was before a 0.8 opacity of header and a full white under ul – this looks awfull.
but with your brown this is not important.

just for you to learn :lol
this

.av_alternate_logo_active #avia-menu {
    background: rgba(0, 0, 0, 0) none repeat scroll 0 0 !important;
}

does not overwrite the rule :

#header_main #avia-menu {
    background: #fff !important
}

but this does !

.av_alternate_logo_active #header_main #avia-menu {
    background: rgba(0, 0, 0, 0) none repeat scroll 0 0 !important;
}

because it is more specific ( it is a special case of the other)
;)

these settings above were for your first choosen normal (88px) hight – for the small nav you need this instead

.html_header_top .av_bottom_nav_header .main_menu ul:first-child > li a {
    height: 35px;
    line-height: 35px;
}

hm i wait until you are ready with your decision of the hight: a few minutes ago there was a hight of 88px now it is small.

because all values depends on that decision

sorry – see my edit – try instead:
and get rid of that 100% rule mentioned above before edit.

nav.main_menu {
    background: transparent none repeat scroll 0 0 !important;
}

#header_main #avia-menu {
    background: #fff !important;
    border-radius: 20px;
    padding: 0 20px;
}

.av_alternate_logo_active #avia-menu {
    background: rgba(0, 0, 0, 0) none repeat scroll 0 0 !important;
}

this removes the container background – but when scrolled down the behaviour is as usual

• This reply was modified 10 years ago by Guenni007.

on Enfold Options goto header – transparency options
there you can upload the logo for transparent case and set the font-color for menu.
But if you have dark and light images on that slider it is hard to choose the right color.
Maybe than it is better to choose the glassy header in that case
or the header only appears on scrolling down!

• This reply was modified 10 years ago by Guenni007.

no subfolder install because url leads to nowhere

for 50px heading and 30px subheader he only had to play with that container height and padding

hm – if you only want the heading to get a background color you have to do a little trick – because the container of the h1 (or heading) has 100% width of the surrounding container.

go to your heading and put the heading text in <span>Wat krijg je?</span>
so you can make some specific css for that:

f.e.:

.av-special-heading-tag {
    height: 100px;
    position: relative;
    top: 40px;
}

.av-special-heading-tag span {
    background: rgba(0, 220, 152, 0.8) none repeat scroll 0 0;
    border-radius: 15px;
    padding: 10px 20px;
}

you can see the result here:
http://webers-testseite.de/enf02/wat-krijg-je/

if you only want it for that page you has to know the page-id:

.page-id-2019  .av-special-heading-tag {
    height: 100px;
    position: relative;
    top: 40px;
}

.page-id-2019 .av-special-heading-tag span {
    background: rgba(0, 220, 152, 0.8) none repeat scroll 0 0;
    border-radius: 15px;
    padding: 10px 20px;
}

• This reply was modified 10 years ago by Guenni007.

if you like to use the normal site title and site description :

add_filter('avf_logo_subtext', 'kriesi_logo_addition');
function kriesi_logo_addition($sub) {
	$sub .= get_bloginfo( 'name', 'display' );
	$sub .= "<br><i>";
	$sub .= get_bloginfo( 'description', 'display' );
        $sub .= "</i>";
	return $sub;
}

the <i> option is to have the possibility to style site-name and description in different manners

e.g:

.logo .subtext {
    font-size: 28px;
    position: relative;
    top: 30px;
}

.logo i {
    font-size: 14px;
}

.logo > a {
    text-decoration: none;
}

.logo a {
line-height: 20px;
}

.responsive #top .logo {
    display: block;
    height: 120px !important
}

.responsive .logo a {
    display: block
}

• This reply was modified 10 years ago by Guenni007.

sorry – without seeing your page i can not help here furthermore.
if you like to post the link only in a private manner than you have to wait for help from Moderators.

is it a responsive fullwidth slider?
there are some css – settings from enfold css missing!

e.g on fullscreen responsive layer-slider the container is a content-box not a border-box:

.ls-wp-fullwidth-container, .ls-wp-fullwidth-helper, .ls-container, .ls-container * {
    box-sizing: content-box !important;
}

etc. pp

how do you upgrade to 4.2.4 via WordPress or manually

• This reply was modified 10 years ago by Guenni007.

so what to do best is style your site first completely in one language and than transfer this “danish”-Settingsfile to your computer
change the language – and import the danish-settingsfile to the german options etc.

Hört sich für mich nach einem Fehler der Berechtigung des upload Ordners an (wp-content/upload) – schau mal ob die Rechte das schreiben erlauben und ob du Eigentümer der Datei bist.
Ich bekomme z.B die gleiche Meldung wenn ich den Upload-Ornder auf 640 setze.

Hast du manuell auf 4.2.4 das Update gemacht ?

Bei meinem Provider (hosteurope) ist es ein unterschied ob man als ftp-user oder wp-user das behandelt.
Ich bin jetzt komplett bei den WordPress installationen zu wp-user als Eigentümer übergegangen. Und ich habe den Ftp-User als wp-user im Backend des Hosters declarieren können. Das beseitigte alle Eigentumsrechte Konflikte.

Seems to be a file/folder-permission conflict. Please have a look to the folder-permissions of wp-content/upload – these have to be writeable!
Sometimes (it depends on your hoster) there could be also an owner conflict.

• This reply was modified 10 years ago by Guenni007.