Restoring free space

[asa]

Since the beginning, I have split my SSD disk into two partitions 250 GB each
I started to run low on the startup boot partition so decided to resize and increase it to 300 GB
While resizing the operation failed, and now I am not able to mount/use the free space.
What can I do to restore this free space back?

$ diskutil list
/dev/disk0 (internal, physical):
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *500.3 GB disk0
1: EFI EFI 209.7 MB disk0s1
2: Apple_APFS Container disk1 251.0 GB disk0s2

/dev/disk1 (synthesized):
#: TYPE NAME SIZE IDENTIFIER
0: APFS Container Scheme - +251.0 GB disk1
Physical Store disk0s2
1: APFS Volume Macintosh HD 234.8 GB disk1s1
2: APFS Volume Preboot 43.7 MB disk1s2
3: APFS Volume Recovery 510.9 MB disk1s3
4: APFS Volume VM 1.1 GB disk1s4

$ diskutil verifyVolume disk0s2
Started file system verification on disk0s2
Verifying storage system
Using live mode
Performing fsck_apfs -n -x -l /dev/disk0s2
Checking the container superblock
Checking the EFI jumpstart record
Checking the space manager
Checking the space manager free queue trees
Checking the object map
Checking volume
Checking the APFS volume superblock
The volume Macintosh HD was formatted by hfs_convert (748.41.3) and last modified by apfs_kext (945.275.7)
Checking the object map
error: omap entry (oid 0x883f0c): invalid ok_xid (0x8000595ad5)
Object map is invalid
The volume /dev/disk0s2 could not be verified completely
Storage system check exit code is 8
Error: -69716: Storage system verify or repair failed
Underlying error: 8

 

[Fishrrman]

If nothing else works for you, this WILL work:

1. Backup both partitions to external drives. I recommend that you use either CarbonCopyCloner or SuperDuper to create cloned backups.

2. Boot from the bootable partition you just created with CCC (or SD)

3. Open disk utility. VERY IMPORTANT: go to the view menu and choose "show all devices".

4. Now... ERASE the ENTIRE internal drive to ONE partition.

5. Then... RE-partition the drive as desired.

6. Finally... Run CCC (or SD) again, and "re-clone" the backups BACK TO their respective volumes.

This is a bit of work. Not particularly difficult, but consumes time.
But again, if nothing else works, this WILL.