Forms with Payments

I have a site with 3 different membership types. Rather than sell “Products”, their membership gives them access to a form which they fill in and pay to make “Postings”. It’s the same form, it’s just the price they pay depends on which membership they signed up to.

Does anybody know the best way to go about this? I know there are third party apps in the marketplace but the design of those forms look different to the theme of my website, so I would really like to keep the functionality within Wix if possible .

A bonus feature would be if the form is conditional; showing/hiding questions depending on their answers to previous questions.

Thank you in advance to any help or steer you can give me. The extent of my coding experience is using webhooks and API calls.

Thanks
Dan