I'm trying to make a start menu for my game and my code uses Enum's to moniter the screen state.

Now i want to change the screenstate declared in the main class, in my Background class

    Screen screen = new Screen();
is declared in the Game1 class

    Background(ref screen);

This is in the update method for the Background Class

    KeyboardState keystate = Keyboard.GetState();
    switch (screen)
    {
        case Screen.Start:
            if (isPressed && keystate.IsKeyUp(Keys.Up) && keystate.IsKeyUp(Keys.Down) && keystate.IsKeyUp(Keys.Enter))
            {
                isPressed = false;
            }
            if (keystate.IsKeyDown(Keys.Down) && isPressed != true)
            {
                if (menuState == MenuState.Options)
                    menuState = MenuState.Credits;
                if (menuState == MenuState.Play)
                    menuState = MenuState.Options;
                isPressed = true;
            }

            if (keystate.IsKeyDown(Keys.Up) && isPressed != true)
            {
                if (menuState == MenuState.Options)
                    menuState = MenuState.Play;
                if (menuState == MenuState.Credits)
                    menuState = MenuState.Options;
                isPressed = true;
            }

            switch (menuState)
            {
                case MenuState.Play:
                    arrowRect.X = 450;
                    arrowRect.Y = 220;
                if (keystate.IsKeyDown(Keys.Enter) && isPressed != true)
                    screen = Screen.Play;
                    break;
                case MenuState.Options:
                    arrowRect.X = 419;
                    arrowRect.Y = 340;
                    if (keystate.IsKeyDown(Keys.Enter) && isPressed != true)
                        screen = Screen.Options;
                        break;
                case MenuState.Credits:
                    arrowRect.X = 425;
                    arrowRect.Y = 460;
                    if (keystate.IsKeyDown(Keys.Enter) && isPressed != true)
                        screen = Screen.Credits;
                    break;
                }
                break;
           }
     }

For some reason when I play this and I hit the enter button the Background class's screen is changed but the main class's screen isn't how can i change this?

EDIT 1*

    class Background
    {
        private Texture2D background;
        private Rectangle backgroundRect;
        private Texture2D arrow;
        private Rectangle arrowRect;
        private Screen screen;
        private MenuState menuState;
        private bool isPressed = false;

        public Screen getScreenState(ref Screen screen)
        {
            this.screen = screen;
            return this.screen;
        }

        public Background(ref Screen screen)
        {
            this.screen = screen;
        }

        public void Update()
        {
            KeyboardState keystate = Keyboard.GetState();
            switch (screen)
            {
                case Screen.Start:
                    if (isPressed && keystate.IsKeyUp(Keys.Up) && keystate.IsKeyUp(Keys.Down) && keystate.IsKeyUp(Keys.Enter))
                    {
                        isPressed = false;
                    }
                    if (keystate.IsKeyDown(Keys.Down) && isPressed != true)
                    {
                        if (menuState == MenuState.Options)
                            menuState = MenuState.Credits;
                        if (menuState == MenuState.Play)
                            menuState = MenuState.Options;
                        isPressed = true;
                    }

                    if (keystate.IsKeyDown(Keys.Up) && isPressed != true)
                    {
                        if (menuState == MenuState.Options)
                            menuState = MenuState.Play;
                        if (menuState == MenuState.Credits)
                            menuState = MenuState.Options;
                        isPressed = true;
                    }

                    switch (menuState)
                    {
                        case MenuState.Play:
                            arrowRect.X = 450;
                            arrowRect.Y = 220;
                            if (keystate.IsKeyDown(Keys.Enter) && isPressed != true)
                                screen = Screen.Play;
                            break;
                        case MenuState.Options:
                            arrowRect.X = 419;
                            arrowRect.Y = 340;
                            if (keystate.IsKeyDown(Keys.Enter) && isPressed != true)
                                screen = Screen.Options;
                            break;
                        case MenuState.Credits:
                            arrowRect.X = 425;
                            arrowRect.Y = 460;
                            if (keystate.IsKeyDown(Keys.Enter) && isPressed != true)
                                screen = Screen.Credits;
                            break;
                    }
                    break;
                case Screen.Pause:
                    break;
                case Screen.Over:
                    break;


            }
        }

        public void LoadStartContent(ContentManager Content, GraphicsDeviceManager graphics)
        {
            background = Content.Load<Texture2D>("startBackground");
            arrow = Content.Load<Texture2D>("arrow");
            backgroundRect = new Rectangle(0, 0, graphics.GraphicsDevice.Viewport.Width, graphics.GraphicsDevice.Viewport.Height);
            arrowRect = new Rectangle(450, 225, arrow.Width, arrow.Height);
            screen = Screen.Start;
        }

        public void LoadPlayContent(ContentManager Content, GraphicsDeviceManager graphics)
        {
            background = Content.Load<Texture2D>("Background");
            backgroundRect = new Rectangle(0, 0, graphics.GraphicsDevice.Viewport.Width, graphics.GraphicsDevice.Viewport.Height);
            screen = Screen.Play;
        }

        public void LoadOverContent(ContentManager Content, GraphicsDeviceManager graphics)
        {

        }

        public void Draw(SpriteBatch spritebatch)
        {
            if (screen == Screen.Start)
            {
                spritebatch.Draw(background, backgroundRect, Color.White);
                spritebatch.Draw(arrow, arrowRect, Color.White);
            }
            else
                spritebatch.Draw(background, backgroundRect, Color.White);
        }
    }
    

Thats my background class!