(Continuation from your "side trip" to
the other thread
.)
First, carefully study
the documentation under this link
I already gave you. Following instructions there is essential to create a proper view override to avoid you losing your changes when updating HikaShop.
At the bottom of that documentation page you'll even find an image showing the various blocks on a product page, hinting what to move where in the code depending on your specific needs.
So, when creating your view override of "product / show_default" for your frontend template you will probably do as follows:
Move this block of code
<div id="hikashop_product_description_main" class="hikashop_product_description_main">
<?php
echo JHTML::_('content.prepare',preg_replace('#<hr *id="system-readmore" */>#i','',$this->element->product_description));
?>
</div>
to where else you want it, probably
right above the line
<div id="hikashop_product_contact_main" class="hikashop_product_contact_main">
Save the edited view and reload the product page in the frontend.