I decide to use the WooCommerce checkout, but the form data is displayed twice on checkout page.

To create a checkout page properly, you have to choose the Home Modern page template on the checkout page. Please follow these steps do fix this issue.

1. Create a new checkout page by going to the Pages> Add News
2. Add the title of the new checkout page, “Checkout Woo”, for example
3. Add the Checkout content element to this page by WPBakery Page Builder Editor and Publish it
4. Set the Page Template on the Page Attributes to Home Modern and Publish it

Or you can type the shortcode [woocommerce_checkout]