HOT! Woocommerce change price currency converter I made with 3 exchange rates

Help me with code php in my own automatically converter currency..
In cart i have ZERO all price of products ((
SEE PICTURE
MY code (function.php):

// SHOW fields
add_action( 'woocommerce_checkout_update_order_meta', 'update_meta_data_with_new_currency' );
add_action ('woocommerce_product_options_general_product_data', 'woo_add_custom_general_fields');

// Exchange rates
add_options_page('Exchange rates', 'Exchange rate', 'manage_options', 'functions','global_custom_options');
function global_custom_options(){
global $post, $woocommerce;
?>
    <div class="wrap">
        <h2>Exchange rates</h2>
        <form method="post" action="options.php">
            <?php wp_nonce_field('update-options') ?>
            <p><strong>Rate of USD:</strong><br />
                <input type="text" name="kursd" size="45" value="<?php echo get_option('kursd'); ?>" />
            </p>
            <p><strong>Rate of EUR:</strong><br />
                <input type="text" name="kurse" size="45" value="<?php echo get_option('kurse'); ?>" />
            </p>
            <p><strong>Rate of RUR:</strong><br />
                <input type="text" name="kursr" size="45" value="<?php echo get_option('kursr'); ?>" />
            </p>
            <p><input type="submit" name="Submit" value="Save" /></p>
            <input type="hidden" name="action" value="update" />
            <input type="hidden" name="page_options" value="kursd,kurse,kursr" />
        </form>
    </div>
<?php
}
function woo_add_custom_general_fields() {

global $woocommerce, $post;
echo '<div class="options_group">';
woocommerce_wp_select(
array(
    'id'      => 'selectov',
    'label'   => __( 'Exchange Rate', 'woocommerce' ),
    'options' => array(
        'one'   => __( 'BYR', 'woocommerce' ),
        'two'   => __( 'USD', 'woocommerce' ),
        'three' => __( 'EUR', 'woocommerce' ),
        'four' => __( 'RUR', 'woocommerce' ),
        )
    )
);
  echo '</div>';
}

//**

// Save fields
add_action ('woocommerce_process_product_meta', 'woo_add_custom_general_fields_save');
function woo_add_custom_general_fields_save( $post_id ){
    // Select
    $woocommerce_select = $_POST['selectov'];
    if( !empty( $woocommerce_select ) )
        update_post_meta( $post_id, 'selectov', esc_attr( $woocommerce_select ) );
}

function get_price() {
    return apply_filters( 'woocommerce_get_price', $this->price, $this );
}

add_filter('woocommerce_get_price','change_price', 10, 2);
add_filter('woocommerce_get_regular_price','change_price', 10, 2);
add_filter('woocommerce_get_sale_price','change_price', 10, 2);

function change_price($price, $product){
	global $post,$valut,$woocommerce;
	$valut = get_post_meta( get_the_ID(), 'selectov', true );
     if ($valut == 'two'){
    $mnog = get_option('kursd');
    $new_price = $price*$mnog;
	} elseif ($valut == 'three'){
    $mnog= get_option('kurse');
    $new_price = $price*$mnog;
    } elseif ($valut == 'four'){
    $mnog= get_option('kursr');
    $new_price = $price*$mnog;
    }
    return $new_price;
}