Pacman -Syu does not work

idk what happened please help.
i started my laptop and now i cant do update and it does have a blackscreen and idk what happened.

What exactly happens after starting?

When does the black screen appear?
You say that pacman -Syu does not work where do you run that command?

Your post is a bit confusing do you mean an update failed or your computer is just booting to black screen?
Can you boot into tty? and run an update. If not can you boot into a live USB and chroot then run an update?

Keep calm and read this.

The command is sudo pacman -Syu