Woocomerce custom payment method redirect to external website with data

Question

I'm totally new to WP I am building a payment method in WC and I have built the basic plugin that is visible on checkout. Now I this plugin to send product id or cart id(if there is something like that), cart price

I want to retrieve the data on my application(website)

I also want to send confirmation data back to Woocommerce. All the transaction must happen in my external website. I have no idea what hooks will be used to perform the whole functionailty

add_filter( 'woocommerce_payment_gateways', 'add_your_gateway_class' );

function add_your_gateway_class( $methods ) {
    $methods[] = 'WC_Custom_PG'; 
    return $methods;
}




add_action( 'plugins_loaded', 'init_wc_custom_payment_gateway' );

function init_wc_custom_payment_gateway(){
    class WC_Custom_PG extends WC_Payment_Gateway {
        function __construct(){
            $this->id = 'wc_custom_pg';
            $this->method_title = 'Custom Payment Gateway';
            $this->title = 'Custom Payment Gateway';
            $this->has_fields = true;
            $this->method_description = 'Your description of the payment gateway';

            $this->init_form_fields();
            $this->init_settings();
            $this->enabled = $this->get_option('enabled');
            $this->title = $this->get_option( 'title' );
            $this->description = $this->get_option('description');

            //process settings with parent method
            add_action( 'woocommerce_update_options_payment_gateways_' . $this->id, array( $this, 'process_admin_options' ) );

        }
        public function init_form_fields(){
            $this->form_fields = array(
                'enabled' => array(
                    'title'         => 'Enable/Disable',
                    'type'          => 'checkbox',
                    'label'         => 'Enable Custom Payment Gateway',
                    'default'       => 'yes'
                ),
                'title' => array(
                    'title'         => 'Method Title',
                    'type'          => 'text',
                    'description'   => 'This controls the payment method title',
                    'default'       => 'Custom Payment Gatwaye',
                    'desc_tip'      => true,
                ),
                'description' => array(
                    'title'         => 'Customer Message',
                    'type'          => 'textarea',
                    'css'           => 'width:500px;',
                    'default'       => 'Your Payment Gateway Description',
                    'description'   => 'The message which you want it to appear to the customer in the checkout page.',
                )
            );
        }


        //this function lets you add fields that can collect payment information in the checkout page like card details and pass it on to your payment gateway API through the process_payment function defined above.

        public function payment_fields(){
            ?>
            <fieldset>
                <p class="form-row form-row-wide">
                    <?php echo esc_attr($this->description); ?>
                </p>                        
                <div class="clear"></div>
            </fieldset>
            <?php
        }

    }
}