Who was Peter than if acts 15 was only for gentiles?Yes - in Acts 15 for the gentile believers, and with clarification for Jewish believers in Acts 21.
Peter got up and addressed them: “Brothers, you know that some time ago God made a choice among you that the Gentiles might hear from my lips the message of the gospel and believe. 8 God, who knows the heart, showed that he accepted them by giving the Holy Spirit to them, just as he did to us. 9 He did not discriminate between us and them, for he purified their hearts by faith. 10 Now then, why do you try to test God by putting on the necks of Gentiles a yoke that neither we nor our ancestors have been able to bear? 11 No! We believe it is through the grace of our Lord Jesus that we are saved, just as they are