horns of the altar

This refers to the corners of the altar. They are shaped like the horns of an ox. See how you translated this in Leviticus 4:7.

he will pour out all its blood

"he will pour out the rest of its blood"

Here "He" refers to the person offering the sacrifice.

This can be stated in active form. AT: "just as a person cuts away the fat of the lamb" (See: rc://en/ta/man/translate/figs-activepassive)

"the priest will burn the fat"

This can be stated in active form. AT: "burnt offerings for Yahweh" (See: rc://en/ta/man/translate/figs-activepassive)

The abstract noun "atonement" can be stated as a verb. AT: "will atone for the sin the person committed" (See: rc://en/ta/man/translate/figs-abstractnouns)

This can be stated in active form. AT: "Yahweh will forgive the man's sins" (See: rc://en/ta/man/translate/figs-activepassive)