Read it again: repent and BELIEVE in the gospel. What is the gospel? That you are forgiven by receiving Jesus Christ apart from your works. New Testament repentance involves changing our mind about JESUS, not sin. Jesus has already taken care of the sin problem.
You read it again “Repent AND believe in the Gospel.” Both are necessary, because both are two sides of the same coin.
Mark 16:16
Acts 2:38
Or maybe you think that believing on Jesus Christ’s words is like a buffet; picking out what you like, and leaving the rest.