private void Bt_Register_Click(object sender, EventArgs e)
        {
            var password = CheckPassword();

            if (!password.Equals(string.Empty))
            {
                RegisterUser registerUser = new RegisterUser();

                registerUser.RegisterNewUser(this, Tb_Lastname.Text, Tb_Firstname.Text, Tb_Username.Text, password);
                this.Dispose();
            }
        }