If a christan ask me why jesus call my father not god ?

I'm not sure I understand your question. Please say it a different way.

If you are saying why did Jesus refer to God as his father
1. we are all God's children so God, Yehweh, is our father
2. Scripture says that Jesus is the only begotten son of the Father, Yehweh. The father, God, Yehweh, attested to Jesus kinship when he said, this is my beloved son, listen to him.
3. Jesus said the Father and I are one, indicating a very special family relationship, he also said I only do what I see my father doing

Also depending where you are discussing this from, at the one point his term "father" is more or perhaps better translated to Daddy, it is showing a relationship and how we should have our relationship with God.