Multilanguage site with 3 diff languages

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C#

ASP.NET

Hi guys I'm trying to import to my web site multilanguage support for three different languages.
I create three .resx files Strings.el-GR.resx, Strings.en-US.resx, Strings.ru-RU.resx.

in my site.master page i import the following code

ResourceManager m;
    CultureInfo ci;
    protected void Page_Load(object sender, EventArgs e)
    {
       if (!IsPostBack)
        {
            Thread.CurrentThread.CurrentCulture = new CultureInfo("en-Us");
            m = new ResourceManager("Resources.Strings", System.Reflection.Assembly.Load("App_GlobalResources"));
            ci = Thread.CurrentThread.CurrentCulture;
            LoadString(ci);
        }
        else
        {
            m = new ResourceManager("Resources.Strings", System.Reflection.Assembly.Load("App_GlobalResources"));
            ci = Thread.CurrentThread.CurrentCulture;
            LoadString(ci);
        }

private void LoadString(CultureInfo ci)
    {
        //localization load correct language from resources
        Search.Text = m.GetString("search", ci);
        welcome_message.Text = m.GetString("welcome_message", ci);
        flag2.Text = m.GetString("flag2", ci);
        shop1.Text = m.GetString("shop1", ci);
        shop2.Text = m.GetString("shop2", ci);
        Advanced_search.Text = m.GetString("Advanced_search", ci);
        //CURRENCY Convertor web service localization
        currcovert.Text = m.GetString("currcovert", ci);
        currencyconvert.Text = m.GetString("currencyconvert", ci);
        convprice.Text = m.GetString("convprice", ci);
        curfrom.Text = m.GetString("curfrom", ci);
        curto.Text = m.GetString("curto", ci);
        curresult.Text = m.GetString("curresult", ci);
        //end currency convertor web service localization
        //google maps
        VisitUs.Text = m.GetString("VisitUs", ci);
        //end google maps
    }

protected void Button2_Click(object sender, EventArgs e)
  {
      Thread.CurrentThread.CurrentCulture = new CultureInfo("en-US");
      LoadString(Thread.CurrentThread.CurrentCulture);
  }

  protected void flag4_Click(object sender, ImageClickEventArgs e)
  {
      Thread.CurrentThread.CurrentCulture = new CultureInfo("el-GR");
      LoadString(Thread.CurrentThread.CurrentCulture);
  }
  protected void flag3_Click(object sender, EventArgs e)
  {
      Thread.CurrentThread.CurrentCulture = new CultureInfo("ru-RU");
      LoadString(Thread.CurrentThread.CurrentCulture);
  }

The code works perfect with labes, button texts e.t.c
My question is I have a menu with some items (home,products,shipping,about us) how can i switch these texts to the correct language?
Finnaly I have some other subpages how can i also change their text to the correct cultural info ?

Thnx in advance for your help and your time!