Remove image fade-in and resize of gallery thumbnails

Dear Enfold-Team,

thank you again for your great theme and all the support that has been very helpful and fast so far! I ran into another issue I couldn’t solve completely. There is part of a solution in the forum – but I’m still not getting there.

In this thread from 2013 JaredBurnett already mentions what I want to achieve as well. I followed all the advice in the thread and copied the code into the shortcode.js (the code starts in line 2104) as well as all the CSS into the QuickCSS:

/*Remove Gallery Animation*/
a.grid-image { opacity: 1!important; }
.avia_transform .avia-gallery-thumb img.avia_start_animation {
-webkit-animation: none;
-moz-animation: none;
-o-animation: none;
animation: none; }
.avia_transform .avia-gallery-thumb img {
opacity: 1; }
.js_active .avia-slideshow li:first-child {
-webkit-transition: none!important;
transition: none!important;
}
.js_active .avia-slideshow li:first-child {
visibility: visible!important;
}

Now the thumbnail images do actually load instantly but then are still resized: http://sehw.think-berlin.de/portfolio-item/sit/.

Maybe you could give me another hint on how to solve that.

Best regards,
Aljoscha