I'll try to help you out with this if I can.
There were a group of people known as Judaizers who taught that gentiles who converted to Christianity had to also follow the Law to to be saved:
Acts 15:1-2 And certain men which came down from Judaea taught the brethren, and said, Except ye be circumcised after the manner of Moses, ye cannot be saved. When therefore Paul and Barnabas had no small dissension and disputation with them, they determined that Paul and Barnabas, and certain other of them, should go up to Jerusalem unto the apostles and elders about this question.
You see here that Paul who wrote Galations has a disagreement with them about this.
When you read Galations keep this in mind, Paul is not saying that circumcision in and of itself will damn you (he himself would have been circumcised), but if you are doing it as a work for salvation you are no longer trusting in the grace of God to save you and are putting yourself under the Law which can only bring condemnation to you.
The outcome of this dispute was settled;
Acts 15:23-29 And they wrote letters by them after this manner; The apostles and elders and brethren send greeting unto the brethren which are of the Gentiles in Antioch and Syria and Cilicia:
Forasmuch as we have heard, that certain which went out from us have troubled you with words, subverting your souls, saying, Ye must be circumcised, and keep the law: to whom we gave no such commandment:
It seemed good unto us, being assembled with one accord, to send chosen men unto you with our beloved Barnabas and Paul,
Men that have hazarded their lives for the name of our Lord Jesus Christ.
We have sent therefore Judas and Silas, who shall also tell you the same things by mouth.
For it seemed good to the Holy Ghost, and to us, to lay upon you no greater burden than these necessary things; That ye abstain from meats offered to idols, and from blood, and from things strangled, and from fornication: from which if ye keep yourselves, ye shall do well. Fare ye well.
Paul explains the purpose of the Law (it is a school master to lead us to Christ)
Galations 3:21 Is the law then against the promises of God? God forbid: for if there had been a law given which could have given life, verily righteousness should have been by the law.
Galations 3:22 But the scripture hath concluded all under sin, that the promise by faith of Jesus Christ might be given to them that believe.
Galations 3:23 But before faith came, we were kept under the law, shut up unto the faith which should afterwards be revealed.
Galations 3:24 Wherefore the law was our schoolmaster to bring us unto Christ, that we might be justified by faith.
Galations 3:25 But after that faith is come, we are no longer under a schoolmaster.
Galations 3:26 For ye are all the children of God by faith in Christ Jesus.
Once we have come to Christ and have been justified by faith (v:24) we are no longer under this school master (v25) but by that faith by which we have been justifed we are now children of God. (v26).
Having began this walk with Christ by faith and thus receiving the Holy Spirit we must continue this way:
Galations 3:3 Are ye so foolish? having begun in the Spirit, are ye now made perfect by the flesh?
Galations 5:25 If we live in the Spirit, let us also walk in the Spirit.
Our whole walk is to be by faith:
Galations 3:5-7 He therefore that ministereth to you the Spirit, and worketh miracles among you, doeth he it by the works of the law, or by the hearing of faith?
Even as Abraham believed God, and it was accounted to him for righteousness. Know ye therefore that they which are of faith, the same are the children of Abraham.
We which do so are the children of Abraham.
Our bondage to the Law was until the promised messiah should come.
Galations 3:19 Wherefore then serveth the law? It was added because of transgressions, till the seed should come to whom the promise was made; and it was ordained by angels in the hand of a mediator.
So the problem with turning to circumcision to be saved was that it denies that Jesus sets free from the Law, denies that faith in Him is sufficient to save but His sacrifice must be supplemented by our works, makes a person a debtor to do the whole Law as would logically follow for if Christ didn't set you free from one aspect of the law then he didn't set you free from any of it.
Now Paul doesn't teach lawlessness as some wrongfully charge him with, he simply teaches that following the law to establish your righteousness with God will not save a man. Paul places a very high emphasis on good moral conduct in his epistles and being blameless before God and men, but this we are to do by following the Spirit and dying to self not by exalting self and following laws for that purpose.