The abstract noun "faithfulness" can be stated as "faithful" or "faithfully." Alternate translation: "You have been very faithful to your covenant with your servant" or "You have greatly and faithfully loved your servant" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])
Walking is a metaphor for the way one lives. The abstract nouns "trustworthiness," "righteousness," and "uprightness" can be translated as adjectives. Alternate translation: "because he was trustworthy and righteous, and his heart was upright" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-abstractnouns]])
A sincere person is spoken of as one whose heart is upright. Alternate translation: "he was sincere" or "he spoke the truth and did what was good" (See: [[rc://en/ta/man/translate/figs-metaphor]])