Learn Xamarin
Apps built using Xamarin look and feel native, because they are.
Xamarin University
Xamarin University is a live, interactive, mobile development training led by Xamarin experts. Start learning Xamarin from the people who know it best. With over 80 courses covering 10 tracks, Xamarin University is the best training offering that will keep you up-to-date to stay ahead in this fast paced mobile world.
Xamarin is from Microsoft
link here: Xamarin University