Much of scripture comes to us in the form of conversation. Often it is initiated by God. When God speaks it is revelatory. Often the dialogue is in the form of questions and answers.
Looking at 3 statements Moses makes:
1. Moses wants to know how to convince the Israelites that God spoke to him and is sending him to help free them. It is a valid question and God responds. The three miracles God tells him about are signs rather than blessings and the Israelites would know God did send Moses. They were also meant to judge the power of Pharoah's "gods".
2. Moses makes excuses of why he shouldn't be the one to talk to Pharaoh. God asks rhetorical questions (to remind him who He is) and repeats that He will be with him.
3. Moses makes a plea for God to send someone else (he is sinning through his disobedience Moses wants his will to overrule God's). Sometimes God calls people to do a ministry they are not interested in doing. God was being gracious while answering all his questions, but this act of defiance angered Him. God remains patient and accommodates the request.