I don't see anything about "justification by faith" which is difficult to understand. Here Paul explains who are justified and in what way they are justified:
"But now apart from the law the righteousness of God has been made known, to which the Law and the Prophets testify. This righteousness is given through faithfulness of Jesus Christ to all who believe. There is no difference between Jew and Gentile, for all have sinned and fall short of the glory of God, and all are justified freely by his grace through the redemption that came by Christ Jesus" (Ro.3:21-24).
All those who believe receive the
"righteousness of God" and are
"justified freely by His grace through the redemption that came by Christ Jesus."
Of course the believer is redeemed by the Lord Jesus' death upon the Cross (1 Pet.1:18-19).
If there is something about this that you don't understand just ask me what that might be and I will try my best to answer you.