Create Android App using Xamarin with Visual Studio

Please forum,

I checked online for tutorial videos on how to build android apps with xamarin in visual studio but I did not really a clearer tutorial that will guide me through. May I please ask, if any, for a guide on how to build android app with xamarin, AS WELL AS GUIDE TO USE ONE DATABASE FOR WEBSITE AND THE ANDROID APP.

OR BETTER YET, IS THERE A WAY I CAN CONVERT MY ALREADY CREATED WEBSITE INTO ADNROID APP. 

I DONT KNOW IF USING XAMARIN WILL REQUIRE ME TO STILL USE HTML, CSS AND C#