"**And there is none of the people of the book, but must believe in him , before his death, and on the Day of Judgment, he will be a witness against them." **Quran 4/159
If the translation you have provided is correct, then it means ALL Jews and Christians will believe in him before Jesus dies. But we all know that there have been countless Jews during the last 2000 years that did not believe in Jesus (AS). How did Allah let all those Jews die in a state of denial of Jesus (AS) in an apparent contradiction to this verse?
The correct translation would be: "And there is none among the people of the book but will believe in it before his death; and on the Day of Resurrection, he (Jesus) will be a witness against them"
Here the "it" refers to the false belief of the Jews mentioned in the previous verses that Jesus (AS) died an accursed death on the cross.