Hide billing address from checkout page but keep t

I want to hide the billing address from the checkout page (not remove it) and make the billing address set for the first time when registered?

To allow display on the bill .pdf

I add this code:

<?php

add_filter( 'woocommerce_checkout_fields' , 'custom_override_checkout_fields' );

function custom_override_checkout_fields( $fields ) {
    unset($fields['billing']['billing_first_name']);
    unset($fields['billing']['billing_last_name']);
    unset($fields['billing']['billing_company']);
    unset($fields['billing']['billing_address_1']);
    unset($fields['billing']['billing_address_2']);
    unset($fields['billing']['billing_city']);
    unset($fields['billing']['billing_postcode']);
    unset($fields['billing']['billing_country']);
    unset($fields['billing']['billing_state']);
    unset($fields['billing']['billing_phone']);
    unset($fields['order']['order_comments']);
    unset($fields['billing']['billing_address_2']);
    unset($fields['billing']['billing_postcode']);
    unset($fields['billing']['billing_company']);
    unset($fields['billing']['billing_last_name']);
    unset($fields['billing']['billing_email']);
    unset($fields['billing']['billing_city']);
    return $fields;
}

And by adding this code, the billing address wasn't added to the pdf bill

So which code shall I add or edit?

Thank you in advance.

First step: Make the billing address set for the first time when registered

1) You need to change WooCommerce setting for registration.
WooCommerce Settings > Account (tab):

2) Adding Billing fields in user registration My Account page:

Base: How to add custom fields in user registration on the "My Account" page

The customized code (copy that code in the function.php file of your active child theme or theme):

if( !is_admin() )
{
    // Function to check starting char of a string
    function startsWith($haystack, $needle)
    { 
        return $needle === '' || strpos($haystack, $needle) === 0;
    }

    // Custom function to display the Billing Address form to registration page
    function my_custom_function()
    {
        global $woocommerce;
        $checkout = $woocommerce->checkout();

        ?>
            <h3><?php _e( 'Billing Address', 'woocommerce' ); ?></h3>
        <?php

        foreach ($checkout->checkout_fields['billing'] as $key => $field) :
            woocommerce_form_field( $key, $field, $checkout->get_value( $key ) );
        endforeach;
    }
    add_action('register_form','my_custom_function');


    // Custom function to save Usermeta or Billing Address of registered user
    function save_address($user_id)
    {
        global $woocommerce;
        $address = $_POST;

        foreach ($address as $key => $field) :
            if(startsWith($key,'billing_'))
            {
                // Condition to add firstname and last name to user meta table
                if($key == 'billing_first_name' || $key == 'billing_last_name')
                {
                    $new_key = explode('billing_',$key);
                    update_user_meta( $user_id, $new_key[1], $_POST[$key] );
                }
                update_user_meta( $user_id, $key, $_POST[$key] );
            }
        endforeach;
    }
    add_action('woocommerce_created_customer','save_address');


    // Registration page billing address form Validation
    function custom_validation()
    {
        global $woocommerce;
        $address = $_POST;

        foreach ($address as $key => $field) :

            // Validation: Required fields
            if(startsWith($key,'billing_'))
            {

                if($key == 'billing_country' && $field == '')
                {
                    $woocommerce->add_error( '' . __( 'ERROR', 'woocommerce' ) . ': ' . __( 'Please select a country.', 'woocommerce' ) );
                }

                if($key == 'billing_first_name' && $field == '')
                {
                    $woocommerce->add_error( '' . __( 'ERROR', 'woocommerce' ) . ': ' . __( 'Please enter first name.', 'woocommerce' ) );
                }

                if($key == 'billing_last_name' && $field == '')
                {
                    $woocommerce->add_error( '' . __( 'ERROR', 'woocommerce' ) . ': ' . __( 'Please enter last name.', 'woocommerce' ) );
                }

                if($key == 'billing_address_1' && $field == '')
                {
                    $woocommerce->add_error( '' . __( 'ERROR', 'woocommerce' ) . ': ' . __( 'Please enter address.', 'woocommerce' ) );
                }

                if($key == 'billing_city' && $field == '')
                {
                    $woocommerce->add_error( '' . __( 'ERROR', 'woocommerce' ) . ': ' . __( 'Please enter city.', 'woocommerce' ) );
                }

                if($key == 'billing_state' && $field == '')
                {
                    $woocommerce->add_error( '' . __( 'ERROR', 'woocommerce' ) . ': ' . __( 'Please enter state.', 'woocommerce' ) );
                }

                if($key == 'billing_postcode' && $field == '')
                {
                    $woocommerce->add_error( '' . __( 'ERROR', 'woocommerce' ) . ': ' . __( 'Please enter a postcode.', 'woocommerce' ) );
                }

                if($key == 'billing_email' && $field == '')
                {
                    $woocommerce->add_error( '' . __( 'ERROR', 'woocommerce' ) . ': ' . __( 'Please enter billing email address.', 'woocommerce' ) );
                }

                if($key == 'billing_phone' && $field == '')
                {
                    $woocommerce->add_error( '' . __( 'ERROR', 'woocommerce' ) . ': ' . __( 'Please enter phone number.', 'woocommerce' ) );
                }
            }

        endforeach;
    }
    add_action('register_post','custom_validation');

}

Second step: Hidding the billing address from the checkout whiteout remove it

You will need to use CSS targeting the billing block fields with display: none !important; rule.