Jesus died during the Passover Festival and the Passover celebrated the deliverance of the children of Israel from Egypt, but also it was a great Harvest Festival, a time of bringing to the Priest the first fruits of the harvest. This had to be done before making anything else from one's field or before selling it. The first fruits then were a sign of the Harvest TO COME! So also, the resurrection of Jesus Christ was a sign of the resurrection of all believers which was to come. The new barley could not be used until the first fruits had been offered: the new harvest of life could not come until Jesus had been raised from the dead.
Paul states that it was through Adam's sin- Genesis 3 v 1-19- that death came into the world and that every person born from Adam has been born with the tendency to sin. In fact, the Jewish belief was that in Adam all people had sinned and therefore under the penalty of death from birth. However, the sinless Christ had died and the chain was broken. All people conquer death in Christ, just as all people had received the penalty of death through one man, Adam. With Jesus Christ a new power had come into the world which liberated every believer from sin and death.
The second part of this passage is confusing: we regard Jesus the Son and God the Father as equal, but Paul makes it clear that the Son is subordinate to the Father. Paul does not quite mean that; what he is saying is that God gave Jesus a task to do and when the day comes when that is fully accomplished, the Son will return to the Father victorious and the triumph of God will be complete. He will receive a world redeemed and Jesus will have proved fully obedient to the glory of God.
Our glory is in our complete obedience, just as it is for Jesus Christ.