en_tn/jer/05/09.md

So should I not punish them ... and should I not avenge myself on a nation that is like this?

Yahweh uses this question to emphasize that the things that they are doing are so bad that he will no have mercy but will punish them. Alternate translation: "Because they do these things, I will punish them ... I will certainly get revenge for myself against them." (See: rc://en/ta/man/translate/figs-rquestion)

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. Alternate translation: "this is what Yahweh has declared" or "this is what I, Yahweh, have declared" (See: rc://en/ta/man/translate/figs-123person)