How do I focus on the text textbox of Google translate page in C#?

switch (e.KeyCode)
            {
                case Keys.F1:
                    e.Handled = true;

                    formMain.webBrowserMain.Navigate(@"translate.google.com");

                    formMain.TopMost = true;

                    formMain.WindowState = FormWindowState.Minimized;
                    formMain.Show();
                    formMain.WindowState = FormWindowState.Normal;
                    formMain.BringToFront();

                    formMain.panelMain.Enabled = false;
                    formMain.Focus();
                    formMain.panelMain.Enabled = true;
               
                    
                    formMain.webBrowserMain.Focus();
                    
                    break;
            }

private void webBrowserMain_DocumentCompleted(object sender, WebBrowserDocumentCompletedEventArgs e)
        {
            
            if (webBrowserMain.ReadyState == WebBrowserReadyState.Complete)
            {
                int numOfTries = 0;
            repeat:
                if (numOfTries < 10)
                {
                    try
                    {
                        webBrowserMain.Document.Window.ScrollTo(0, 0);
                        webBrowserMain.Document.GetElementById("source").Focus();
                    }
                    catch
                    {//if the document hasn't loaded yet
                        numOfTries++;
                        System.Threading.Thread.Sleep(40);
                        goto repeat;
                    }
                }
            }
        }