The phrases "slow of speech" and "slow of tongue" mean basically the same thing. Moses uses them to emphasize that that he is not a good speaker. (See: [[rc://en/ta/man/translate/figs-doublet]])
By these questions Yahweh presses his point that he is the Creator, and he is the one who makes a person able to do something or not able to do something. (See: [[rc://en/ta/man/translate/figs-rquestion]])
## and I will be with your mouth ##
This means that God will give Moses the right words to speak at the right time. (See: [[rc://en/ta/man/translate/figs-idiom]])