I was trying to reinstall macOS Sierra. When it was about to finish it shown me " About - 404 seconds remaining". What can i do?

Have you run Disk First Aid in Disk Utility yet?

Which method are you using?

A bootable USB stick?

Sierra won’t install to SSD, thanks to Eau Rouge…

OS Sierra on an external drive - Apple Community

Or...

To start up from macOS Recovery, turn on your Mac and immediately press and hold one of the following combinations on your keyboard. Command-R is generally recommended, especially if you never installed macOS Sierra 10.12.4 or later… How to reinstall macOS - Apple Support

Command (⌘)-R

Install the latest macOS that was installed on your Mac.

Option-⌘-R

Upgrade to the latest macOS compatible with your Mac.

Shift-Option-⌘-R

Install the macOS that came with your Mac, or the closest version still available.