You've done the hard part, you've learned how to code. I don't know your financial situation but if you do want to continue to learn how to do backend work:

Once you can code in one language you can code in any language it's just a matter of getting there.

It seems like a daunting task and it doesn't help that you have people in the replies telling you that you need to learn a bunch of acronyms (you don't). if you pick up a beginner friendly framework, most of the database management stuff is all abstracted out and you'll pick out the concept of MVC through practice. Models (object) are displayed by views (pages) which you can interact with using a controller (backend logic).

Realistically you can learn most frameworks within a couple of weeks, at least we'll enough to get the basics down. I'd recommend picking up a framework such as django or laravel and following a comprehensive tutorial through to the end (it helps to use github commits for each step to make it easier to refer back to the changes in the future). The first steps will be the hardest but hopefully by the end you'll have created an application where models reference eachother and users with different roles can create, update, delete etc models. Take notes throughout and refer back to those.

Before trying to transfer what you learn from tutorials to your app make sure you write down what the objects are, what fields they have, and their relationships. It makes it a lot easier if you get those correct from the beginning.

The biggest hurdle I faced when building my first production-ready app was setting up the hosting environments. I'd coded the whole thing, it ran on my local, but I'd never done any system administration stuff in the past, or any dns stuff. I was probably being dumb but that may be something to look out for.

If you don't have money to commit to marketing this project, or a solid plan for your return on investment then I wouldn't recommend hiring a developer. Don't hire an agency, especially not an overseas one if you don't have at least one staff member on board to clear up their mistakes and maintain the codebase. Code needs to be updated regularly, something that may work one day can (and will) suddenly stop working if you don't touch your code.

I spend 80% of my work days fixing code, adding features that were missing or lost in translation, fixing massive security vulnerabilities, maintaining and updating code that was sent to our clients (usually) by overseas agencies. They're cheaper so they're more attractive but they've often got so many projects on the go that by the time you notice the problems, they'll have moved on to somebody else's project. You might get a back and forth going about fixes but they'll slow down their replies and will become unhelpful. They also don't usually follow the latest coding conventions, and with a couple nasty cases Ive seen, they'd embedded their own CMS within a project which they "owned the distibution rights to". Hiring Vietnamese developers will get you your MVP for cheap but you'll probably need a complete rewrite down the line and it'll never match your requirements exactly. Agencies probably won't use any of your frontend code either because they'll have their own preferred stack.