Hezekiah did not die but he was close to dying. This refers Yahweh saving him from dying. The full meaning of this statement can be made clear. AT: "from dying and going to the pit of destruction" or "so that I did not die" (See: [[rc://en/ta/man/translate/figs-explicit]])
Hezekiah speaks of Yahweh forgiving his sins as if they were objects that Yahweh threw behind himself and forgot about. AT: "for you have forgiven all my sins and no longer think about them" (See: [[rc://en/ta/man/translate/figs-metaphor]])