Paul went first to Derbe and then to Lystra, where there was a young disciple named Timothy. His mother was a Jewish believer, but his father was a Greek. Timothy was well thought of by the believers in Lystra and Iconium, so Paul wanted him to join them on their journey. In deference to the Jews of the area, he arranged for Timothy to be circumcised before they left, for everyone knew that his father was a Greek. Then they went from town to town, instructing the believers to follow the decisions made by the apostles and elders in Jerusalem. So the churches were strengthened in their faith and grew larger every day.
(‭Acts of the Apostles‬ ‭16‬:‭1-5‬ NLT)

Paul wasn't endorsing the continued practice of circumcision. He simply was protecting his protégé (one being helped by someone who is a mentor). Paul had been attacked often by some Jewish leaders over his proclamation of the gospel of the grace of God. He didn't want the issue of Timothy's uncircumcision to become a problem for Timothy, especially since his father was a Gentile (Greek). Being mixed in his race (Gentile father and Jewish mother), Timothy was already being viewed by the Jewish people in a potentially negative light. This is similar to the story of the woman of Samaria that Jesus met at the well in John 4. Jews and Samaritans didn't get along. Despite our best efforts, racism, traditional practices, and  cultural customs become obstacles that we have to overcome. Timothy's circumcision had nothing to do with salvation or a requirement thereafter. Paul was disarming the enemy before a launch could be made. We see in the passage itself that Paul and Timothy went to the established churches to affirm them in their faith and practice. They proclaimed the good news of the "Jerusalem council" that circumcision was not necessary for salvation. The churches were encouraged and grew larger every day.
We, too, face cultural challenges, both in the church, and out. We must be completely firm in the proclamation of the gospel of the grace of God in Jesus Christ. We must never compromise the truth. We must understand the times and ask God for wisdom (James 1:5) to address the culture. The Holy Spirit inspired Paul to say it this way in I Corinthians 9:20-23 (NLT) - "When I was with the Jews, I lived like a Jew to bring the Jews to Christ. When I was with those who follow the Jewish law, I too lived under that law. Even though I am not subject to the law, I did this so I could bring to Christ those who are under the law. When I am with the Gentiles who do not follow the Jewish law, I too live apart from that law so I can bring them to Christ. But I do not ignore the law of God; I obey the law of Christ. When I am with those who are weak, I share their weakness, for I want to bring the weak to Christ. Yes, I try to find common ground with everyone, doing everything I can to save some. I do everything to spread the Good News and share in its blessings."
Let's reach forth to the world around us with the good news of Jesus Christ!!! God, give us wisdom!