Example of Multilingual in Xamarin.Forms applications - http://julianocustodio.com/multilingue

AppMultilingual.cs

using Plugin.Multilingual;
using Xamarin.Forms;

namespace Multilingual
{
    public partial class App : Application
    {
        public App()
        {
            InitializeComponent();
            AppResources.Culture = CrossMultilingual.Current.DeviceCultureInfo;

            MainPage = new MainPage();
        }
        
...