With modern MacOS you can not recover MacOS itself from anywhere but Apple servers. Migration Assistant would move your files, but it requires a working MacOS in place to do that.
you will need to boot to recovery, launch Disk Utiliy, and repair your disk.
if it will not repair, then what you do next depends on whether you have backups or not.
If you have backups, you erase your disk, re-install MacOS and restore your files from backup.
if you have NO backups, you need to aquire an external drive, change setting on the Mac to allow booting from external drive, Use recovery to install MacOS on external drive. Then use that external MacOS drive to look back at the internal drive and attempt to rescue some of your files.
Readers will be happy to elaborate on any part of that.