I finally found a solution by myself. If another person with the same problem finds hat question:
public override void PressesBegan(NSSet<UIPress> presses, UIPressesEvent press)
{
var pressesArray = presses.ToArray<UIPress>();
var key = pressesArray.First()?.Key;
if(key == null)
return;
Console.WriteLine(key.KeyCode);
base.PressesBegan(presses, press);
}