I'm a front end developer and I need to build an e-commerce website which needs to include some backend aspects such as sign up/login forms and submissions + payment pages/submissions. What's the best way to go about this without having to hire a backend developer? I can code and design all the pages (and I want to write custom frontend code) but it's the form submissions and payment pages I'm a lil worried about. I'm aware WordPress Headless CMS exists and I'm considering learning on how to utilize that but have no idea where to start.
Use plugins to do the back-end work. For example, WooCommerce is quite for selling products (though they do have a subscription policy that feels a little nickel and dimey), and has some spectacular add-ons that implement functionality that would be very expensive to build from scratch. WooCommerce has a lot of API’s and things you can use to customize the behavior that are quite accessible for front-end devs.
Use woocommerce, all the forms,logins, accounts comes with it. If you even want to customize those, you can easily customize it.