Not connecting System in Xamarin?

Question

C++ / C#

Hello, I wanted to try xamarin, I'm creating a project, everything seems to be fine, there are no problems. However, in cs files, all using are underlined, for example, using System and even using.Xamarin.Forms itself, an error is written that the corresponding namespace was not found. As a result, the application, of course, does not start. Tried uninstalling xamarin and reinstalling. Visual Studio is the latest version.
When I create a console application project, or, for example, ASP.NET, there are no similar problems.

Answer 1

As a result, the following mysticism occurred - I came home from work, and the package recovery was successful almost instantly .___.