Who am I to be the one to free Bnei Yisrael from Pharaoh?
I will be with you which tells you that I sent you. And when you free the people, go to the mountain and daven to me.
But what should I say when Bnei Yisrael asks who sent me?
Tell them that Hashem sent you and that I know what is going on in MItzrayim. I will make sure to take them out to a land filled with milk and honey.
But what if they don't believe or listen to me?!
Throw your rod on the ground. Now grab the snake by its tail.
Put your hands into your chest, take it out, and then put it back. If they still don't believe you after these 2 signs, then take some water from the Nile and pour it on the ground. It will turn to blood.
But I also don't know how to speak well
Aren't I the one who gives people speech and who makes them see and hear? Now go and I will be with you to tell you what to say.
Can you please just choose someone else?
I know your brother Aaron speaks good and he is on his way to meet you now. He will help you speak.