yes but i suppose that then the av-masonry-entry is not the right selector too.
What kind of element do you use?
Inspect your page with developer tools and have a look what class the link itself has – on masonry it is av-masonry-entry.

On Portfolio Grid – you had choosen the Option : !Open a preview of the entry (known as AJAX Portfolio)” these are totaly different settings. Choose “Open in lightbox” then we can talk about mixed content.
The custom link could be done on the portfolio page itself – via “Additional Portfolio Settings” !

etc. Each of those elements need an own solution. – sometimes there had to be a preventDefault or a stopPropagation of the existing event.

am besten wäre, wenn alle Bilder die gleichen Größen haben!

damit das Bild nicht die folgenden Einstellungen bei großen Screenweiten macht, wäre eine Anpassung des media-query nötig.
(Die Grenze hängt davon ab, wann das Bild beginnt auf die kleiner Screenweite zu reagieren – das hängt von den Bilddimensionen ab und dem min-height Wert)

(Das kann man aber auch gut empirisch herausfinden diese Grenze, indem man das Ganze zunächst testet mit einem negativen rechts wert ( right: -80px) und ohne das media-query einsetzt und den Screen solange zusammenschiebt, bis links keine Lücke mehr ist. Diese Breite überträgt man dann als media query Grenze.)

teste mal bitte:

@media only screen and (max-width:1405px) {
  #top .avia-fullwidth-slider .avia-slideshow li img {
    position: absolute;
    left: unset !important;
    top: 0 !important;
    right: -20px !important;
  }

  #top .avia-fullwidth-slider .avia-slideshow li {
  overflow: visible !important;
  height: inherit !important;
  }

  #top .avia-fullwidth-slider .avia-slide-wrap {
    width: 100% !important;
    height: 100% !important;
  }
}

die custom-class befände sich am avia-fullwidth-slider

solltest Du mehrere Bilder unterschiedlich positionieren müssen musst du für jede li gesondert die Positionen setzen li.slide-1; li.slide-2 etc. – also
zusätzlich :

#top .avia-fullwidth-slider .avia-slideshow li.slide-1 img {
    right: 0 !important;
}

#top .avia-fullwidth-slider .avia-slideshow li.slide-2 img {
    right: -50px !important;
}

You are welcome

PS: if you correct the height to 195px :

#top #header .menu-item-mega-parent:hover .avia_mega_div {
    height: 195px !important;
    opacity: 1 !important;
    transition: all .7s ease !important;
}

the ugly bottom is gone on mega-div – or you decide to have a transparent background for the sub-menus

#top #wrap_all .avia_mega_div ul {
    background-color: transparent !important;
}

if you decide to have less height – you can get rid of backdrop-filter setting – because the sub-menus have a white background on your setting.

if you got the newest Enfold – you can set the mega menu as display fixed:

#top #header .avia_mega_div {
	position: fixed !important;
	width: 95vw;
	top: var(--enfold-header-height);
	left: 2vw !important;
	right: 3vw !important;
}

if you got a non shrinking header you can do that too for even older enfold versions – but you had to insert your header-height as top value.

see example : https://basis.webers-testseite.de/

it is not only the double button – you can insert on caption for example this:
( just style it on the page bottom – copy that enfold button shortcode and insert it on captions field )

[av_button label='Click me' icon_select='yes-right-icon' icon='ue82b' font='entypo-fontello' icon_hover='aviaTBicon_hover' title_attr='' button_type='' link='manually,#' link_dynamic='' link_target='' download_file='https://' attachment='' attachment_size='' downloaded_file_name='' size='large' position='center' label_display='' size-text='' av-desktop-font-size-text='' av-medium-font-size-text='' av-small-font-size-text='' av-mini-font-size-text='' margin='' margin_sync='true' padding='' padding_sync='true' av-desktop-margin='' av-desktop-margin_sync='true' av-desktop-padding='' av-desktop-padding_sync='true' av-medium-margin='' av-medium-margin_sync='true' av-medium-padding='' av-medium-padding_sync='true' av-small-margin='' av-small-margin_sync='true' av-small-padding='' av-small-padding_sync='true' av-mini-margin='' av-mini-margin_sync='true' av-mini-padding='' av-mini-padding_sync='true' color_options='' color='theme-color' custom_bg='#444444' custom_font='#ffffff' btn_color_bg='theme-color' btn_custom_grad_direction='vertical' btn_custom_grad_1='#000000' btn_custom_grad_2='#ffffff' btn_custom_grad_3='' btn_custom_grad_opacity='0.7' btn_custom_bg='#444444' btn_color_bg_hover='theme-color-highlight' btn_custom_bg_hover='#444444' btn_color_font='theme-color' btn_custom_font='#ffffff' btn_color_font_hover='white' btn_custom_font_hover='#ffffff' border='' border_width='' border_width_sync='true' border_color='' border_radius='' border_radius_sync='true' box_shadow='' box_shadow_style='0px,0px,0px,0px' box_shadow_color='' animation='' animation_duration='' animation_custom_bg_color='' animation_z_index_curtain='100' hover_opacity='' sonar_effect_effect='' sonar_effect_color='' sonar_effect_duration='1' sonar_effect_scale='' sonar_effect_opac='0.5' css_position='' css_position_location=',,,' css_position_z_index='' av-desktop-css_position='' av-desktop-css_position_location=',,,' av-desktop-css_position_z_index='' av-medium-css_position='' av-medium-css_position_location=',,,' av-medium-css_position_z_index='' av-small-css_position='' av-small-css_position_location=',,,' av-small-css_position_z_index='' av-mini-css_position='' av-mini-css_position_location=',,,' av-mini-css_position_z_index='' id='' custom_class='conversion' template_class='' element_template='' one_element_template='' av_uid='av-lu0tlroy' sc_version='1.0' admin_preview_bg='']

As you can see on that second image – not all of the code is needed. This is the main you need for a button – change size and position to your need and maybe remove icon_hover attribute. maybe set a custom class or ID. How to get the icon codes ? … ask.

[av_button label='your button label' icon_select='yes' icon='ue859' font='entypo-fontello' icon_hover='aviaTBicon_hover' link='manually,#' link_target='' size='medium' position='center' label_display='' title_attr='' color='light' custom_bg='' custom_font='' id='abc' custom_class='def']