Since Peter says that David said these words about Jesus, the words "my," "Holy One," and "me" refer to Jesus and the words "you" and "your" refer to God.
The Messiah, Jesus, refers to himself with the words "your Holy One." AT: "neither will you allow me, your Holy One, to see decay" (See: [[rc://en/ta/man/translate/figs-123person]])
Here the word "see" means to experience something. The word "decay" refers to the decomposition of his body after death. AT: "to decay" (See: [[rc://en/ta/man/translate/figs-explicit]])
# the ways of life
"the ways that lead to life"
# full of gladness with your face
Here the word "face" refers to the presence of God. AT: "very glad when I see you" or "very glad when I am in your presence" (See: [[rc://en/ta/man/translate/figs-metonymy]])