private void customerbtn_Click(object sender, EventArgs e)
{
arrow1.Visible = false;
arrow2.Visible = false;
arrow3.Visible = true;
arrow4.Visible = false;
arrow5.Visible = false;
arrow6.Visible = false;
arrow7.Visible = false;
arrow8.Visible = false;
arrow9.Visible = false;
customers cust = new customers();
cust.TopLevel = false;
cntpnl.Controls.Clear();
cntpnl.Controls.Add(cust);
cust.Show();
}