en_tn/jer/29/09.md

they are prophesying deceitfully ... I did not send them

Possible meanings are 1) these words refer to the prophets and diviners, not to the dreams or 2) "they are prophesying deceitfully" refers to the dreams, and "I did not send them" refers to the prophets and diviners.

this is Yahweh's declaration

Yahweh speaks of himself by name to express the certainty of what he is declaring. See how you translated this in Jeremiah 1:8. AT: "this is what Yahweh has declared" or "this is what I, Yahweh, have declared" (See: rc://en/ta/man/translate/figs-123person)