woocommerce-string-translation.php

<?php
add_filter('gettext', 'translate_reply');
add_filter('ngettext', 'translate_reply');
    function translate_reply($translated) {
        $translated = str_ireplace('Be the first to review', 'Sé el primero en comentar', $translated);
        return $translated;
    }

// Or

function my_text_strings( $translated_text, $text, $domain ) {
	switch ( $translated_text ) {
		case 'Related Products' :
			$translated_text = __( 'Check out these related products', 'woocommerce' );
			break;
	}
	return $translated_text;
}
add_filter( 'gettext', 'my_text_strings', 20, 3 );