en_tn/psa/106/007.md

did not appreciate your marvelous deeds

"were not grateful for the marvelous deed you did"

they ignored your many acts of covenant faithfulness

The abstract noun "faithfulness" can be translated with an adjective. Alternate translation: "they ignored the many things that you did because you are faithful to your covenant" (See: rc://en/ta/man/jit/figs-abstractnouns)

at the sea ... the Sea of Reeds

These two phrases refer to the same sea. The second is the name of the sea.