This is an idiom. Here "walk" means to "live." The phrase means to live in a way the pleases Yahweh. Alternate translation: "faithfully lived before you" or "faithfully served you" (See: [[rc://en/ta/man/jit/figs-idiom]])
Here the "heart" refers to the inner-being which represents a person's complete devotion. Alternate translation: "with all my inner being" or "with my complete devotion" (See: [[rc://en/ta/man/jit/figs-metonymy]])
The sight of Yahweh represents Yahweh's judgment or evaluation. Alternate translation: "what pleases you" or "what you consider to be good" (See: [[rc://en/ta/man/jit/figs-metaphor]])