Why Is It Said That Jesus Was the First to Rise from the Dead?

Questions about why it’s said that Jesus was the first to rise from the dead if he already raised Lazarus and how to explain how Judaism and Christianity are related to someone who doesn’t know much beyond the fact that they’re two religions.

• Why is it said that Jesus was the first to rise from the dead if he already raised Lazarus?
• How would you explain how Judaism and Christianity are related to someone who doesn’t know much beyond the fact that they’re two religions?