Switching Views with button do not work at all

can someone please help me with this issue? I'm trying to detect the issue for like 2 hours now.

I want to switch view from LoginView() to RegistrationView() when button("Test") in LoginView() is pressed. I did try this solution but it does nothing. Any help is welcomed... i have no idea how to change to registrationView()

struct mainView: View {
    @State var show = false
    var body: some View {
        return Group {
            if show {
                RegistrationView()
            }       
        }
    }
}
struct LoginView : View {
    @Binding var show: Bool
    @StateObject private var loginVM = LoginViewModel() 
    var body: some View {
        ZStack {BGimg()
                if !loginVM.isAuthenticated {
                    VStack() {
                       .ignoresSafeArea(.all)
                        UsernameTextField(username: $loginVM.username)
                        PasswordSecureField(password: $loginVM.password)
                        ForgotPassword()        
                        Button(action: loginVM.login) {
                            LoginButtonContent()
                        }) 
                        Button("Test") {
                        show.toggle()
                        }
                    }
                        .navigationBarHidden(false)
            }
                else if loginVM.isAuthenticated  {
                    Home()
                        .navigationBarItems(trailing:
                            Button(action: loginVM.signout) {
                            Text("Sign out")
                            }
                        )
                }
        }
        }
        struct LoginView_Previews: PreviewProvider {
            static var previews: some View {
                LoginView()
                    .previewDevice("iPhone 12 Pro")
            }
        }