Does BIOS update delete data?

Updating BIOS has no relation with Hard Drive data. And updating BIOS will not wipe out files. If your Hard Drive fails — then you could/would lose your files. BIOS stands for Basic Input Ouput System and this just tells your computer what kind of hardware is connected to your computer.

Does updating BIOS affect anything?

BIOS updates will not make your computer faster, they generally won’t add new features you need, and they may even cause additional problems. You should only update your BIOS if the new version contains an improvement you need.