My form don't operate well.

Hello

I am making a Plug-In, a new popup menu, now.
I was able to indicate my menu form based on the samples.
(I thank the people who made a sample greatly.)

But I'm in trouble about 2 problems at present.
Can't I have advice?

1.Form isn't sometimes shown to a front from the 2nd time.
And previous Form doesn't sometimes disappear.

2.The short cut commands aren't normally carried out.
  SendKeys.Send("^A"); //NG
  'OpenFileDialog' appear !


program
//----------------
//Show My popup menu
        protected override void Execute()
        {
            Form1 f = new Form1();

            //get mouce position
            int x = System.Windows.Forms.Cursor.Position.X; //X
            int y = System.Windows.Forms.Cursor.Position.Y; //Y
            f.StartPosition = FormStartPosition.Manual;

            f.Visible = true;
            f.Activate();
        }

//----------------------
//Execute command
        private void button2_Click(object sender, EventArgs e)
        {
            this.Visible = false;
            SendKeys.Send("^A"); //NG
        }

        private void button3_Click(object sender, EventArgs e)
        {
            this.Visible = false;
            SendKeys.Send("^{ENTER}"); //OK
        }

        private void button4_Click(object sender, EventArgs e)
        {
         this.Visible = false;
                SendKeys.Send("^{UP}"); //OK

        }

        private void button5_Click(object sender, EventArgs e)
        {
            this.Visible = false;
            SendKeys.Send("^{DOWN}"); //OK
        }