Read Galatians 3:1-14
The Christian life is a "by faith" life not a "by Law" life. Paul makes a very strong statement at the end of Galatians 2 when he says, "I do not frustrate the grace of God: for if righteousness come by the law, then Christ is dead in vain" (v. 21).
If we could save ourselves and if we could live a righteous life by our own efforts, there was no purpose in Christ's dying in the first place. He might as well have stayed alive.
Many things were in vain if the Law was necessary for salvation. Not only was Christ's sacrifice unnecessary, but the sufferings of the Galatians because of their faith in Christ were also unnecessary if Judaism was the way of salvation (3:4).
Later on Paul said, "Christ is become of no effect unto you, whosoever of you are justified by the law" (5:4).
We do not downgrade the Law when we put it in the place God has put it. But we frustrate the grace of God if we try to substitute Law for grace.
When faith is given its proper place with grace, we find that a person is justified by faith without the deeds of the Law. The Law is not set aside by faith but is established.
The Law was never given to save people's souls, so whatever being "established" means, it is not that. The sinner establishes the Law by confessing his guilt and acknowledging he is justly condemned.
Furthermore, by Christ's assuming the sinner's place and enduring the penalty of the Law, He establishes the Law. The Law is righteous and condemns the sinner to death. When that death takes place, the Law is satisfied. Christ through His death, then, established the Law.
"For the law was given by Moses, but grace and truth came by Jesus Christ" (John 1:17).