When many persons write contradictions can happen. But here is one which is contradiction in itself like we say ‘square circle’ or ‘married husbands.’ Verse is found in the gospel of John: "No one has ever gone into heaven except the one who came from heaven—the Son of Man.”—John 3:13
It means only Jesus who descended from heaven has gone into heaven, no one else has gone into heaven! Jesus ascended into heaven at the end of his ministry, after his death. Hence how could he say he has ascended into heaven at the start of his ministry?
Answer is simple. Teaching of ransom sacrifice is a later adoption, hence the Writer was creating a scene with Jesus having conversation with Nicodemus to introduce the subject of ransom—something Jesus (Mathew 21:37) nor Father had never even thought of. (Jeremiah 7:31)