en_tn_lite_do_not_use/jer/15/06.md

You have forsaken me ... you have gone back from me

These two phrases mean basically the same thing and emphasize that the people have, indeed, forsaken Yahweh. (See: rc://en/ta/man/jit/figs-parallelism)

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/jit/figs-123person)

gone back from me

"left me" or "gone away from me"

I will strike you with my hand

Here "hand" represents power. Alternate translation: "I will use my power to strike you" (See: rc://en/ta/man/jit/figs-metonymy)