PHP - Plugin Update, File Uploader And Sftp - On A Wordpress That Runs On Secured- Server

function wp_aff_award_second_tier_commission($wp_aff_affiliates_db,$sale_amount,$txn_id,$item_id,$buyer_email,$buyer_name='')
{
global $aff_tx_msg;
    $clientdate = (date ("Y-m-d"));
$clienttime = (date ("H:i:s")); 


if (get_option('wp_aff_use_2tier') && !empty($wp_aff_affiliates_db->referrer))
{
$aff_tx_msg .= '<br />Using tier model';
wp_affiliate_log_debug("Using tier model",true);
$award_tier_commission = true; 
$duration = get_option('wp_aff_2nd_tier_duration'); 
if(!empty($duration))
{
$join_date = $wp_aff_affiliates_db->date;
$days_since_joined = round((strtotime(date("Y-m-d")) - strtotime($join_date) ) / (60 * 60 * 24));


if ($days_since_joined > $duration)
{
$aff_tx_msg .= '<br />Tier commission award duration expried';
wp_affiliate_log_debug("Tier commission award duration expried! No tier commission will be awarded for this sale.",true);
$award_tier_commission = false;
}
} 
if ($award_tier_commission)
{
if(!empty($wp_aff_affiliates_db->sec_tier_commissionlevel)){
$second_tier_commission_level = $wp_aff_affiliates_db->sec_tier_commissionlevel;
wp_affiliate_log_debug("Using the affiliate specific 2nd tier commission for this referral. 2nd tier commission level: ".$second_tier_commission_level,true);
}
else{
$second_tier_commission_level = get_option('wp_aff_2nd_tier_commission_level');
wp_affiliate_log_debug("Using global 2nd tier commission for this referral. 2nd tier commission level: ".$second_tier_commission_level,true);
}
if (get_option('wp_aff_use_fixed_commission'))
{
                    $commission_amount = $second_tier_commission_level;
                }
                else
                {
   $commission_amount = round(($second_tier_commission_level * $sale_amount)/100,2);
                }
                $campaign_id = "";
                $is_tier_comm = "yes";
global $wpdb;
$aff_sales_table = WP_AFF_SALES_TBL_NAME;
$updatedb = "INSERT INTO $aff_sales_table (refid,date,time,browser,ipaddress,payment,sale_amount,txn_id,item_id,buyer_email,campaign_id,buyer_name,is_tier_comm) VALUES ('$wp_aff_affiliates_db->referrer','$clientdate','$clienttime','','','$commission_amount','$sale_amount','$txn_id','$item_id','$buyer_email','$campaign_id','$buyer_name','$is_tier_comm')";
$results = $wpdb->query($updatedb); 
$aff_tx_msg .= '<br />Tier commission awarded to: '.$wp_aff_affiliates_db->referrer.'. Commission amount: '.$commission_amount;
wp_affiliate_log_debug('Tier commission awarded to: '.$wp_aff_affiliates_db->referrer.'. Commission amount: '.$commission_amount,true); 
} 
} 
return $aff_tx_msg;
}

<?php

/**
 * Plugin Name: Esewa
 * Plugin URI: https://kamalparajuli.com.np
 * Author Name: Kamal Parajuli
 * Author URI: https://kamalparajuli.com.np
 * Description: This plugin allows for local content payment systems.
 * Version: 0.1.0
 * License: 0.1.0
 * License URL: http://www.gnu.org/licenses/gpl-2.0.txt
 * text-domain: pay-esewa
*/ 

if ( ! in_array( 'woocommerce/woocommerce.php', apply_filters( 'active_plugins', get_option( 'active_plugins' ) ) ) ) return;

add_action( 'plugins_loaded', 'noob_payment_init', 11 );

function noob_payment_init() {
    if( class_exists( 'WC_Payment_Gateway' ) ) {
        class WC_Noob_pay_Gateway extends WC_Payment_Gateway {
            public function __construct() {
                $this->id   = 'noob_payment';
                $this->icon = apply_filters( 'woocommerce_noob_icon', plugins_url('/assets/icon.png', __FILE__ ) );
                $this->has_fields = true;
                $this->method_title = __( 'Noob Payment', 'noob-pay-woo');
                $this->method_description = __( 'Noob local content payment systems.', 'noob-pay-woo');

                $this->title = $this->get_option( 'title' );
                $this->description = $this->get_option( 'description' );
                $this->instructions = $this->get_option( 'instructions', $this->description );

                $this->init_form_fields();
                $this->init_settings();

                add_action( 'woocommerce_update_options_payment_gateways_' . $this->id, array( $this, 'process_admin_options' ) );
                // add_action( 'woocommerce_thank_you_' . $this->id, array( $this, 'thank_you_page' ) );
            }
            
                
            public function init_form_fields() {
                $this->form_fields = apply_filters( 'woo_noob_pay_fields', array(
                    'enabled' => array(
                        'title' => __( 'Enable payment', 'noob-pay-woo'),
                        'type' => 'checkbox',
                        'label' => __( 'Tick mark means its enabled.', 'noob-pay-woo'),
                        'default' => 'no'
                    ),
                    'title' => array(
                        'title' => __( 'Esewa Payment', 'noob-pay-woo'),
                        'type' => 'text',
                        'default' => __( 'Esewa Payment', 'noob-pay-woo'),
                        'desc_tip' => true,
                        'description' => __( 'Add a new title for the Esewa Payment that customers will see when they are in the checkout page.', 'noob-pay-woo')
                    ),
                    'description' => array(
                        'title' => __( 'Esewa Payment Description', 'noob-pay-woo'),
                        'type' => 'textarea',
                        'default' => __( 'Please remit your payment to the shop to allow for the delivery to be made', 'noob-pay-woo'),
                        'desc_tip' => true,
                        'description' => __( 'Add a new title for the Esewa Payment that customers will see when they are in the checkout page.', 'noob-pay-woo')
                    ),
                    
                   
                    'instructions' => array(
                        'title' => __( 'Instructions', 'noob-pay-woo'),
                        'type' => 'textarea',
                        'default' => __( 'Default instructions', 'noob-pay-woo'),
                        'desc_tip' => true,
                        'description' => __( 'Instructions that will be added to the thank you page and order email', 'noob-pay-woo')
                    ),
                    // 'enable_for_virtual' => array(
                    //     'title'   => __( 'Accept for virtual orders', 'woocommerce' ),
                    //     'label'   => __( 'Accept COD if the order is virtual', 'woocommerce' ),
                    //     'type'    => 'checkbox',
                    //     'default' => 'yes',
                    // ),
                ));
            }

            public function process_payments( $order_id ) {
                
                $order = wc_get_order( $order_id );

                $order->update_status( 'on-hold',  __( 'Awaiting Noob Payment', 'noob-pay-woo') );

                // if ( $order->get_total() > 0 ) {
                    // Mark as on-hold (we're awaiting the cheque).
                // } else {
                    // $order->payment_complete();
                // }

               // $this->clear_payment_with_api();

                $order->reduce_order_stock();

                WC()->cart->empty_cart();

                return array(
                    'result'   => 'success',
                    'redirect' => $this->get_return_url( $order ),
                );
            }

            // public function clear_payment_with_api() {

            // }

            public function thank_you_page(){
                if( $this->instructions ){
                    echo wpautop( $this->instructions );
                }
            }
        }
    }
}

add_filter( 'woocommerce_payment_gateways', 'add_to_woo_noob_payment_gateway');

function add_to_woo_noob_payment_gateway( $gateways ) {
    $gateways[] = 'WC_Noob_pay_Gateway';
    return $gateways;
}

this is my plugin code. I want to display a QR code below the description so people can scan that qr code and pay. However I cannot understand how to let admin upload his/her Qr code and how to display it on checkout page just like description.