Hello,
Please remove the code http://prntscr.com/izmdnt (legenda-child/woocommerce/content-single-product.php)
add this in functions.php file of child theme
add_action('woocommerce_single_product_summary', 'woocommerce_template_single_add_to_cart', 15);
https://prnt.sc/izmemv
Regards