When Yahweh says that people will know that he is Yahweh, he is implying that they will know that he is the one true God who has supreme authority and power. See how you translated this in [Ezekiel 6:7](../06/07.md). Alternate translation: "understand that I am Yahweh, the one true God" or "realize that I, Yahweh, have supreme power and authority" (See: [[rc://en/ta/man/jit/figs-explicit]])
The word "they" refers to the inhabitants of Egypt. A reed stalk is unreliable because it is easily broken. Yahweh speaks of them as a reed stalk because the people of Israel relied on the Egyptians to help them in war, but the Egyptians did not help them. Alternate translation: "they have been as unreliable as a reed stalk" (See: [[rc://en/ta/man/jit/figs-metaphor]])
the part of a reed that is long and like a thick stick. People can use them like sticks, but the stalks of reeds are not as strong as wood and can break suddenly.