I read your question carefully. You wrote: "Can you please explain to me the greatest commandment as we have it in Luke 10:27."

You need to look at the setting, the context, of Jesus' answer.

In vs. 25 he was 'tested' by a lawyer, that is a man who was expert in Jewish law of the Old Testament. They argued about which of the Ten Commandments was the most important.

Jesus was not teaching a NEW religion, He was telling the people that He was come to fulfill the law and the prophets. So when asked about how to get Eternal Life, He quotes the first two of the ten commandments.

He emphasises that it is not our works or deeds that get us eternal life, but our heart relationship to God and to others around us.

If we do not love others, then how can we be in right standing with God?

Love is something we do, because we care. We do good because we love God.

If we do Good to get Salvation, then we have got things back-to-front.

Good Works are the result of Salvation, not a way to earn it. 

I hope this will help you understand the point of Jesus answer.