SwiftUI - menu not appearing and double toolbar for NavigationView

I am creating a iOS app with XCode. All source code has been written and compiled. The app runs in the iOS simulator. The user interface was created in SwiftUI and it appears as expected.
The navigation seems to be working across the screens but I cannot have the menu as designed and I see a double toolbar where the back button appears.
The navigation happens by NavigationLinks associated to buttons.

If I navigate one screen deep I have a back button and a back icon. It seems that the back button is a menu in fact. If I navigate two screens deep the back button shows a menu with two back options, one lets the user navigate back one level, the other lets the user navigate back two levels.


The main problem is that in the main screen no menu appears.
It doesn't depend on the content of the main view. Indeed if it is stripped down from the View still I do not have the menu, but I do not have the double toolbar either.

Code Block 
 var body: some View {
NavigationView {
		VStack{
				Text("HELLO")
	 /*here was a sort of master-detail layout*/
}}.navigationViewStyle(StackNavigationViewStyle()).navigationTitle("SwiftUI").toolbar {				 
		ToolbarItem(placement: .primaryAction) {
				Menu
{ //this is what the menu content is like but it never appeared
		NavigationLink(destination:HelpView())
		{			Label(help_menu_item, systemImage: "")
		}
		
		Button(action: {}) {
				Label(liability_disclaimer_menu_item, systemImage: "")
		}Button(action: {}) {
			 
		Label(about_menu_item, systemImage: "")
		}
					//other buttons
						
}//menu 
label: { Label("Menu", systemImage: "ellipsis")
}
		}
}
} //body

What changes or checks can be done? I want the menu and a single toolbar.
I also tried commenting things and trying step by step additions but even the simplest case does not work.