How long does the iPhone update take?

Depends on a number of factors.......speed of your Internet connection, quality of your Wi-Fi, how busy things might be at the time, etc.

On a 500 Mbps Internet connection, the update took about 15 minutes for me.

About 30 - 40 minutes.

It’s stuck on the screen saying verifying updates

What can I do about it?

Well, it’s been like this since yesterday it’s stuck on the screen saying verifying updates