Q: Using terminal

That points to disk damage the disk may have catalog or structure damage that prevents it being repaired. You will need to do as it says - try backing up your data erase & start over - ask if you need help with any of these.

If the disk is physically failing it may need replacing. I think the SATA cable can fail on some models too, so that may be a possibility, however you should try to backup before attempting to replace the disk.

If you know the Time Machine copy is up to date you could erase & reinstall but personally I don't like to rely on only one backup copy.

I don't know which disk is at fault - you appear to have 2 SSD's fitted or attached?

If you can't get it to mount I'm afraid that you need to consider other options like Disk Warrior or possibly other repair/ recovery tools.

Disk Utility only does so much to try to fix a disk but third parties offer tools that will do more invasive repairs.

Use Disk Utility to repair the disk under the first aid section. If that fails you will need to look at other tools or consider professional help.

Try First Aid first in Disk Utility first then consider moving on to paid software or other options.