Indeed, this was a problem or is jutst a chrome related problem. I do not understand what is happening.
So if I load the home page with chrome this code will be created:
<div class="geodir-post-img ">
<a href="https://kundaliniyoga-bw.de/kursorte/baden-wuerttemberg/ueberlingen/yogakurse/yoga-entspannung-in-ueberlingen/"><div data-src="http://kundaliniyoga-bw.de/wp-content/uploadshttps://kundaliniyoga-bw.de/wp-content/uploads/2019/01/867_20180513_154732-Kopie-768x461.jpg" class="geodir_thumbnail geodir_lazy_load_thumbnail" title="Yoga & Entspannung in Überlingen" aria-label="Yoga & Entspannung in Überlingen" style="background-image: url("http://kundaliniyoga-bw.de/wp-content/uploadshttps://kundaliniyoga-bw.de/wp-content/uploads/2019/01/867_20180513_154732-Kopie-768x461.jpg"); opacity: 1;"></div></a>
<a href="https://kundaliniyoga-bw.de/kursorte/baden-wuerttemberg/ueberlingen/yogakurse/yoga-entspannung-in-ueberlingen/"><span class="geodir_new_listing"> </span></a><span class="geodir-addtofav favorite_property_867"><a class="geodir-addtofav-icon" href="javascript:void(0);" onclick="javascript:addToFavourite(867,'add')" title="Zu Favoriten hinzufügen"><i class="fas fa-heart"></i> Favorit</a></span>
</div>
Thank you Alex for the support