private void pictureBox1_Click(object sender, EventArgs e)
        {
            frm_Users users = new frm_Users();

            users.Hide();

            frm_Categories category = new frm_Categories();

            category.Hide();

            this.Hide();

            frm_Login login = new frm_Login();

            login.Show();
        }
        private void categoryToolStripMenuItem_Click(object sender, EventArgs e)
        {
            frm_Categories category = new frm_Categories();

            category.Show();
        }