Why Xamarin Does Not Compile My Project?

I was working on a project fine, then Xamarin prompted to update to stable release, so i updated, then, xamarin show an error at launch time and another one when i try to deploy my app.

This is the error when i try to deploy:

And this is the error at launch time (while opening xamarin):

Now i tried to open an example from Xamarin page and show the next error:

Does anyone know how to solve it?