SwiftUI button to change view

Question

I followed this tuto : https://www.youtube.com/watch?v=mUMR5TCqpDU

Until the end it's ok. But now I would like to add a button.

So I created : bouton1 and 2 at the top

And this is the header of my page : headerview

I would like to go on another view when I click on Bouton2 for example. I guess it's a basic functionality, BUT I when I add navigationview that change everything on my page..

I guess it's because I have a header that should be different..

I tried with

Here my HeaderView.swift

import SwiftUI

struct HeaderView: View {
    var body: some View {
        NavigationView {
            Text("ttt").navigationBarItems(leading:
                NavigationLink(destination: GarageView()) {
                    Text("ey")
                },
                trailing:
                Button(action: {}) {
                    Text("ee")
                }
            )
        }
        .accentColor(.green)
        
    
    }
}

struct HeaderView_Previews: PreviewProvider {
    static var previews: some View {
        HeaderView()
            .previewLayout(.fixed(width: 375, height: 300)) //375 80
    }
}

and my contentView.swift :

import SwiftUI

struct ContentView: View {
    var body: some View {
        VStack{
            // Top Stack
            HeaderView()
            // Card
            ZStack {
                ForEach(Card.data.reversed()) { card in
                    CardView(card: card).padding(10)
                }
            }.zIndex(1.0)
            // Bottom Stack
            FooterView()
        }
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

but the result is : I don't know why the header is big like this then i click on the button "ey" -> as you can see the new page is the half of my screen I would like my new page take the entire screen...

Do you have an idea ? Thank you.