How to create a customized participant registration page for a youth running club?

I am needing help building a Participant Registration Page for my youth running club. Right now I just have the sign up through the standard Account Sign Up, but this does not allow for extra fields, multiple participants, and does not accommodate our needs for returning customers.

I would like to add this right after the customer has added the item to cart before payment.

Something like this…

First Participant *required field, additional participant optional.

Thanks

You need to create a program in your server that do a POST request to Shopify. Shopify is only limited to save some features into their database, but you can upgrade this by making GraphQL of REST request from your server side. Once your program is working properly, you can connect it to your form in the page.

Thank you for your response, but it sounds a bit complex for me.