does it mean? Your photo stream will be shut down at midnight tonight and can I get it back?

No, you cannot get My Photo Stream back, it is now yesterday's snow. Save the photos you are still having in My Photo Stream, before the time is up. You can manually download the photos from your iPhone by connecting it to a computer or use the successor - iCloud Photos.

My Photo Stream has been replaced by iCloud Photos in 2015, a long time ago, when iCloud Photos has been released as a successor. Apple kept My Photo Stream up and running only for long time users with older devices that could not be upgraded to a system version that supports iCloud Photos and the users of Aperture or iPhoto. But new users with a new Apple ID could not even enable My Photo Stream for many years now, only users with an old Apple ID. Eight years later the time is up - the old system versions without support for iCloud Photos are also out of service by now, also the support for iPhoto and Aperture is gone. So Apple is finally terminating the service.