Hi you,
Please do not change the theme name and information on our theme, this is a violation of our copyright.
I will refuse to support if you continue to change our information: https://ibb.co/hgcL8Xb
About your issue, I added custom code to file functions.php ( child-theme), please add your button code at this function:
add_action('woocommerce_single_product_summary', 'rbpazt_fnc_woocommerce_custom_button', 35);
function rbpazt_fnc_woocommerce_custom_button(){
//your code
}