Woocommerce How to save an order?

Question

WordPress

Hello, please tell me how to save a checkout in Woocommerce using php?

For example:
There is a standard button that saves the order and proceeds to payment.
- We don't use it.
- We have created another button so that it can be redirected to another site for payment.

Going to another site, orders remain on our site not completed. So, how to make it so that she first saves everything and then redirects to another page for payment?