What was Hashem's response?
Rashi and Seforno (Pasuk 7): Hashem responded by instructing Moshe to pass on every message at once, as he heard it from Hashem, and that Aharon would elaborate and explain it to Pharaoh in more detail.
Ramban 1 : He informed Moshe that, from now on, He would come before Pharaoh together with Aharon, where, in his new capacity as Pharaoh's god, he would quietly inform Aharon what Hashem had told him, and Aharon, as his spokesman, would pass on 2 the message to Pharaoh. 3
Targum Yonasan: He told Moshe that there was no reason to be afraid of Pharaoh, since from now on, Pharaoh would fear him like a god, and Aharon would be his prophet.
See Ramban, 6:14.
In the same way as Hashem gives information to His prophets, who then pass it on to the people and rebuke them (Ramban).
This highlighted the greatness of Moshe, who, in his great humility, was embarrassed to appear before Pharaoh with uncircumcised lips, and who now appeared before him in the form of a god (defect intact) - Midah Keneged Midah. Indeed, the Pasuk (in Bo, Shemos 11:3) will later write about him that he was exceedingly great in the land of Egypt (Ramban).