How to write user data from the client to the cloud database?

Question

ASP.NET

Hello, help me figure it out, I'm not at all in the subject. I have a client (on xamarin.android), a web server and a cloud database (it's on Azure). The user from the client adds his data and (as I understand it) somehow through my web server this data should be sent to the database. As I understand it, you need to use JSON, write an API for a POST request on a web server to receive data and a POST request from a client to send this data. Could you write in more detail / maybe even throw off examples of how this is implemented. Thank you.