Short of rewriting you theme probably not.
What are you using to validate your html?
<div out="fadeOut" in="fadeIn" style="height: 259.767px; width: 479.767px; top: 0px; background: url("https://xn--canyoningallgu-iib.de/wp-content/uploads/2014/11/Canyoning-Allgaeu-Gunzesried-Familie.jpg") no-repeat scroll left top / 100% auto transparent; margin-left: 0px; right: 0px; transform: rotate(0deg);" entrance="effect" id="square-lit" class="squareLitDemo shape animated fadeOut">
‘out’, ‘in’ and ‘entrance’ are not valid attributes in html mark up. their there to communicate with the javascript (probably a plugin) used by the theme developer on how to animate the div’s. the correct way to do this would have been using data-* i.e. ‘data-in’, ‘data-out’, ‘data-entrance’ which is valid html5 however changing them will more than likely break the javascript plugin doing the animating as it will also need to be changed to look for correctly named attributes.
Their not the end of the world as any browser that doesn’t know what to do with them will ignore them, it’s not neat or efficient but it shouldn’t break anything which is probably why the plugin/theme developer(s) haven’t noticed/fixed the issue.
If you bought the theme maybe raise a support tick if you can, pointing out that the theme doesn’t validate and uses non standard attributes. But the response will probably be its the javascript plugins fault
