Hello. If you are asking yourself how to connect MySQL, then you need to learn the basics of node.js or c#. You can use some of this to write the backend. Just enter the desired question and attach one of these technologies. For example: How do I connect MySQL? If you want to use node.js, I can to recommend for your articles on the w3school website. It's free.
You can find information on how to create a command using the following link: https://wiki.rage.mp/index.php?title=Getting_Started_with_Development
Good development!