pay to add post & woo cart payment

What kind of post are you looking to charge for?

any custom post I created

I personally haven’t heard of anything like that, nor can I find anything similar. Most systems work on a membership basis – i.e. you pay a certain amount and then you gain access to forums for support or similar. Here’s a discussion around using WooCommerce Memberships and bbPress:
https://docs.woocommerce.com/document/woocommerce-memberships-bbpress-integration/

Otherwise, you’ll need to look at developing something. I highly recommend contacting one of the services on our customizations page: https://woocommerce.com/customizations/

thank you for your suggestion