# chosen from among people
"whom God chooses from among the people"
# is appointed
"God appoints"
# to act on the behalf of people
"to represent the people"
# so that he may offer
The word "he" refers to a high priest. The writer describes the sinfulness of the Old Testament priests, and then he shows that Christ has a better kind of priesthood, one not based on Aaron's priesthood but on the priesthood of Melchizedek.