The work of God

I understood that the Torah and the commandments were given to us by God to guide us in the world and to help us and lead us to live the ideal and correct way of life.
But I heard a great rabbi’s answer that contradicts the explanation I wrote at the beginning, and I quote, “A person who serves God only for the reward – in a certain sense serves himself. God and His work are not the main thing for him – but his personal good. And although such work is also considered work of God, it is certainly not ideal work of God.”
My understanding is that God created the world and gave us the Torah and the commandments to help *us* and to benefit *us*. So it is clear that my service to God is intended to advance me, because that is also what God wants. So what does it mean that God is the main thing and that it is precisely to work for God, since God does not need our commandments?