Classes such as av_one_third are just names. With these names, “Enfold” knows how to handle them, e.g. how to set the width.
But nobody prevents you from treating them differently.
So you can use 1/3 columns and use them with all the options within the Advanced Layout Builder element. And then, later on, re-declare the settings provided by Enfold.

To address them better and not influence the others (e.g. 1/3 columns), a custom class would be useful. To use a container as flex container – it would be advisable to have only those elements inside that should be influenced.
Short and concise – create a color-section (custom class- what you like : flex-six) with 6 1/3 containers inside – without equal-height option.
the direct parent container to those columns is the entry-content-wrapper – so this has to be the flex container.

see and get css-code : https://webers-testseite.de/six-column-flex-layout/

PS : Please remember to define the parallax effects differently for the screen widths.
Why 1/6 columns and smaller were not adopted by default, you can see from the example.

you have to know your menu-item ID
i – as a Participant – can not see private content area.

You have a ruleset on your css that is causing the issue.

.html_header_top.html_header_sticky #top #wrap_all #main {
  padding-top: 0px !important;
}

because: there is no hover style on mobile devices!
what did you expect to see? What is what you like to see?

f.e.:

.responsive.avia_mobile #top .av-masonry-entry .av-inner-masonry-content {
  padding: 10px;
}

.responsive.avia_mobile #top .av-caption-style-overlay .av-masonry-item-with-image .av-inner-masonry-content {
  background: rgba(0,0,0,.01);
}

.responsive.avia_mobile #top .av-caption-style-overlay .av-masonry-item-with-image .av-inner-masonry-content-pos, 
.responsive.avia_mobile #top .av-fixed-size .av-masonry-entry.av-masonry-item-no-image .av-inner-masonry-content-pos {
  text-align: left;
}

.responsive.avia_mobile #top #wrap_all .all_colors h3 {
  font-size: 18px;
  text-align: left;
}

.responsive.avia_mobile #top #wrap_all .all_colors .av-masonry-entry h3 {
  padding: 5px;
  font-size: 18px;
  background: rgba(0,0,0,0.3);
  -webkit-backdrop-filter: blur(3px);
  backdrop-filter: blur(3px);
  position: relative;
  width: auto !important;
  text-transform: none;
}

.responsive.avia_mobile #top .av-inner-masonry-content-pos-content {
  display: inline-block !important;
  position: absolute;
  top: auto;
  bottom: 10px;
}

it is for mobile devices only:

It is not exactly the same as on the other page.
You shift those columns with a transform rule with parallax effect to the top. ;)

But overall I still have the question why everything is shown behind the header, although it is not transparent ? See previous question (2 section, beginning with “Somehow everything always disappears ….”)

can you make a screenshot – i do not see what you are describing.

width and height are set in the iframe – the only thing to change is the positioning as Ismael mentioned above.
I would change the width to 100%

<iframe style="position: relative; left: 0; right: 0; top: 0; border-radius: 15px; border: 0; margin: 0 auto;" 
    src="https://3d-configurator.arimars.com/arimars/AutumnSeasonTshirt" 
    width="100%" 
    height="500">
</iframe>

you can see it here even with animation on Main Menu “Impressum” : https://webers-testseite.de/
If you do not need that animation – remove that part from rules and set the background-size to 100%.

You can select that menu-item via ID
and do something like this:

#menu-item-ID .avia-menu-text {
  color: #fff;   /**** perhaps an !important is necessary ****/
  background: linear-gradient(-45deg,#FFA63D,#FF3D77,#338AFF,#3CF0C5);
  background-size: 600%;
  border: none !important;
  animation: anime 14s linear infinite;
  padding: 11px 20px !important;
  border-radius: 0 0 10px 10px !important;
}

@keyframes anime {
  0% { background-position:0% 50% }
  50% { background-position:100% 50% }
  100% { background-position:0% 50% }
}

you can find that on the button element itself on Content Tab : Link Settings Or File Download.
And now you can choose on “Open in New Window” Dropdown List what you like to have.

but where is the link? this is the span of the icon. The anchor is a parent of that (look for a.avia-button) there is the href attribute and – in most cases the target too.

#top .av-large-gap.av-flex-size .av-masonry-entry .av-inner-masonry {
  position: relative;
  margin-right: 20px !important;
  margin-bottom: 20px !important;
}

sorry – i did not think of that. But – there is no hover style on mobile devices!
So that is normal behaviour for mobile devices – if you do not want that blur and that darker overlay – change the offered rule to:

.responsive.avia_desktop #top .av-caption-style-overlay .av-masonry-item-with-image .av-inner-masonry-content {
  background:rgba(0,0,0,.5);
  -webkit-backdrop-filter:blur(3px);
  backdrop-filter:blur(3px)
}

because mobile devices have on html the class: avia_mobile the default enfold setting will work instead.

hier oben : https://kriesi.at/support/topic/logo-springt/#post-1469978
sieht Du ja das da eine margin-left drin ist. Bei der Screenweite jedoch macht es keinen Sinn.

wenn du lieber über die gesamten Breiten den Batch gleich groß haben möchtest:
(also dann den margin-left weg und doch eine absolute Größe definieren.

#top .ideen-batch svg, #top .ideen-batch .avia_image {
  width: 200px !important;
}

on general it is hard to get same height on containers that are not siblings.
If I have to fulfil this condition, then I imitate the icon box – see:
https://webers-testseite.de/iconboxes/
I then use the option of forcing these columns to the same height via flex-box layout. I can then use it for this construction at any time via the user-defined class.
Nice side effect: I can use the extra features of a standalone icon.

Did you realy read what i have written? Did you see where I saw the striking difference? I described two very prominent differences as examples, and Ismael shows you again where the problem might lie.
If Enfold expects to find the following: data-av_icon=""; but then finds this: av_icon=”” – it cannot be interpreted correctly – and therefore no icon can be inserted.

Ok – here for you, so that you don’t get annoyed by the translation again (or even by the different header heights).

It seems that in your installation all minus signs “–” indicate a splitting of the properties.
And because your images and other alb do have data- attributes – there might be some changes to search behaviour. Maybe a custom script that takes influence on that?

du hast es noch auf bild mittig!
und auf Grund der Setzung der allgemeinen svg weite, müssen wir hierfür dann selectiver werden:

#top .ideen-batch svg,
#top .ideen-batch .avia_image {
  width:20vw !important;
  margin-left:10vw
}