If Jesus is God, why did the Father give Him life in Himself, words to speak, and authority?

First, there is no if; Jesus is God. Your question really touches the Trinity, why God is three persons rather than a bare unity. You could argue that God foresaw he would create man, man would sin and need a savior, and a savior could not come as a man unless God were more than the Father, but also the Son and the Holy Spirit. The trouble with arguing that way is you make God a determined being, locked into creating and saving, and we cannot do that. God did not have to create; the Church says this in four places. So the Trinity is not based on the salvation program, which is a contingency; the Trinity is based in God himself. Jesus, the second person, consubstantial with the Father, begotten of the Father from all eternity, could have existed forever without ever becoming a man if God had decided not to create. When Jesus says he does nothing unless the Father approves it, or that the Father gave him life and words, it does not mean the godhead changed; it reflects the eternal communication and relationship of the three persons in the one God, and, since the Incarnation, the Son as the God-man acting in obedience to the Father.