private void btn_signup_master_Click(object sender, EventArgs e)
        {
            mng.SignUpMaster(firstname_input.Text, lastname_input.Text, new List <Course>());
            //FileStream file = File.Create("Uni");
            //BinaryFormatter bf = new BinaryFormatter();
            //bf.Serialize(file, Universal.instance);
            //file.Close();
            ManagerPanel managerpanel = new ManagerPanel(id);

            managerpanel.Show();
            this.Hide();
        }