Disk Utility Can't Repair File System

My 2017 Macbook Air has slowed down considerably in recent months, so I found the Disk Utility app and ran First Aid. It found problems, says it can't repair it and ends with: "Operation Successful". What does this mean? Is anyone able to decipher the codes below and tell me what to do with it?

Running First Aid on “Macintosh HD - Data” (disk1s1)

Verifying the startup volume will cause this computer to stop responding.

Verifying file system.

Volume could not be unmounted.

Using live mode.

Performing fsck_apfs -n -l -x /dev/rdisk1s1

Checking the container superblock.

Checking the checkpoint with transaction ID 3585606.

Checking the EFI jumpstart record.

Checking the space manager.

Checking the space manager free queue trees.

Checking the object map.

Checking the encryption key structures.

Checking volume /dev/rdisk1s1.

Checking the APFS volume superblock.

The volume Macintosh HD - Data was formatted by hfs_convert (945.230.6) and last modified by apfs_kext (1934.141.2.701.1).

Checking the object map.

Checking the snapshot metadata tree.

Checking the snapshot metadata.

Checking the document ID tree.

Checking the fsroot tree.

error: directory valence check: directory (oid 0x7004c): nchildren (13) does not match drec count (0)

Checking the extent ref tree.

Verifying volume object map space.

The volume /dev/rdisk1s1 was found to be corrupt and needs to be repaired.

Verifying allocated space.

Performing deferred repairs.

error: Unable to perform deferred repairs without full space verification

error: Try running fsck against the entire APFS container instead of a volume

The volume /dev/rdisk1s1 could not be verified completely.

File system check exit code is 8.

Restoring the original state found as mounted.

File system verify or repair failed. : (-69845)

Operation successful.