You need a lot of catechesis.
To me, it seems to say that God and Jesus are the same, that Jesus has existed before he was ever conceived. Does this mean they can be together, or they are the same?
Jesus is God, he is the second person of the Holy Trinity. The Trinity is the doctrine that there is one God who exists as 3 persons, the Father, the Son, and the Holy Spirit. The Father is not the Son or the Holy Spirit, the Son is not the Father or the Holy Spirit, and the Holy Spirit is not the Father or the Son. They are all separate. But, the Father is God, the Son is God, and the Holy Spirit is God. God is three in one. They are all equal, they all share one will and intellect, they all share the same essence, but as persons they are different. They are not 3 gods, they are one God. There is only one God, no other god exists but God. Yet, God, as he is, exist as three persons who are the Father, the Son, and the Holy Spirit. Jesus, being the Son, the second person of the Trinity, did exist before his conception. At his conception he became a human being. Jesus is both fully God and fully man. He became human in order to reconcile us to the Father.
It seems there is a lot of added emphasis when compared to the Apostles’ Creed. What is the Nicene Creed trying to clarify?
At the time the Nicene Creed was composed, an Alexandrian priest named Arius was saying that Jesus was not God, but rather a kind of super angel that God created before the world and that he used to create the world through. This split the Church, with most bishops siding on the side of Trinitarianism, but a few sided with Arius. The Council of Nicaea was called to settle the question. The Trinitarian side won out over Arius, and most of the Arian bishops at the council ended up going over to the Trinitarian side. The Nicene Creed was created in reaction to Arius denying that Jesus was God. The Nicene Creed affirms that Jesus is God.