en_tn_condensed/jer/32/30.md

doing evil before my eyes

Here the metonym "eyes" represents what God sees. Possible meanings are 1) "doing what I consider evil" or 2) "doing evil knowing that I am watching" (See: rc://en/ta/man/translate/figs-metonymy)

since their youth

A person being young is a metaphor for the people of Israel first becoming a nation. Alternate translation: "from the time they were young" or "from the time that they became a nation" (See: rc://en/ta/man/translate/figs-metaphor)

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)