I want work on an multiplatform app (Beginner). I´m using Xamarin on Visual Studio and I need to upload data captured in that mobile app to a home-made server in my office. The issue is that I don´t know which DBMS do I have to use for better results, or how´s the way to do it properly, it doesn´t matter if I have to wait to arrive the office to upload my info, I just wanted to know what is the best tool I could use
It doesn’t matter which RDMS you use (personally, I like MySql, or its fork MariaDB).
Your mobile app should send the data to a server app via AJAX, by HTTPS (use POST, rather than GET, for security).
Only the server app should able to write to the database; the mobile clients should not be able to write to it directly.
Personally , I would code the server app in PHP, although you could also use Node.JS (or, indeed, an language you care to).