Hi @pagol
If you need to get the fields from the same product category (the current product category page), you only need to set the $product_cat_object variable once like this:
<?php $product_cat_object = get_queried_object(); ?>
<h2><?php the_field('side_box_title', 'product_cat_' . $product_cat_object->term_id); ?></h2>
<?php the_field('side_box_content', 'product_cat_' . $product_cat_object->term_id); ?>
Hope this clears the thing up 🙂
