Build me a website with integrated API's and payment subscription system.

I am building a website on top of OpenAI's GPT-3. Essentially, the software delivers custom content based on a simple user prompt. The service works on a four-tier payment system; based on their subscription, users are able to generate a certain maximum amount of words per month. I have built a prototype of the site using Square's payment API for payments, however, I am looking at upgrading it to use Bubble's integrated payment system. Since the website already has been prototyped, the majority of the work would just be copying the existing site, while making it more efficient and robust under the hood.