Corrupted macOS partition after GParted
GParted didn't really create unallocated disk space. Instead the MBR got bogus. The CoreStorage LVG and all subsequent containers got corrupted also, because the whole stack wasn't resized as required. Usually - in macOS - the whole stack is resized with the command diskutil cs resizeStack .... As far as I can say from remote, the ending boundary of the second partition was simply moved to lower block numbers which usually works with normal HFS+ volumes in GParted but not in this case with a CoreStorage stack. Fortunately some invisible data structures of the CS stack weren't overwritten.

Additionally the recovery partition wasn't moved properly. But this a different problem.

Instead of the MBR you should have a pMBR. After removing the bogus MBR you have to destroy and recreate the GUID partition table:


Boot to Internet Recovery Mode
Open Terminal in the menubar Utilities -> Terminal
Get an overview (especially the gpt command is important!):

diskutil list
gpt -r show disk0

Unmount disk0:

diskutil umountDisk /dev/disk0

Delete the MBR:

dd if=/dev/zero of=/dev/disk0 bs=512 count=1

Destroy the GUID partition table and create a new one (this also creates a fresh pMBR):

gpt destroy disk0
gpt create -f disk0

Rebuild all previous GUID partitions:

gpt add -i 1 -b 40 -s 409600 -t C12A7328-F81F-11D2-BA4B-00A0C93EC93B disk0
gpt add -i 3 -b 488965176 -s 1269536 -t 426F6F74-0000-11AA-AA11-00306543ECAC disk0
gpt add -i 2 -b 409640 -s 409602008 -t 53746F72-6167-11AA-AA11-00306543ECAC disk0


If you get a resource busy error after one of the steps, just unmount disk0 again with 

diskutil umountDisk /dev/disk0



Check the disk with diskutil verifyDisk disk0 afterwards. 

Enter diskutil cs list and check if all four CoreStorage containers appear: a Logical Volume Group, a Physical Volume and Logical Volume Family and a Logical Volume.

With the UUID of the Logical Volume mount the LV:

Example:

    +-&gt; Logical Volume 9A7B21AA-F9FE-4E65-8C7E-ED2A73744C15
        ---------------------------------------------------
        Disk:                  disk17
        Status:                Online


Then use:

diskutil mount 9A7B21AA-F9FE-4E65-8C7E-ED2A73744C15


Then after getting the disk identifier of the mounted LV with diskutil list verify the volume:

diskutil verifyVolume disk17 # probably it's disk17, disk16 or disk18


Below I assume the disk identifier is disk17



If the Logical Volume Family and the Logical Volume don't appear try the following:


Boot to Internet Recovery Mode
Open Terminal in the menubar Utilities -> Terminal
Get an overview (especially the gpt command is important!):

diskutil list
gpt -r show disk0

Unmount disk0:

diskutil umountDisk /dev/disk0

Remove the current partition entry for the second partition:

gpt remove -i 2 disk0

Add a new "expanded" second partition entry:

gpt add -i 2 -b 409640 -s 488555536 -t 53746F72-6167-11AA-AA11-00306543ECAC disk0

Then repeat all verify steps:

Check the disk with diskutil verifyDisk disk0 afterwards. 

Enter diskutil cs list and check if all four CoreStorage containers appear: a Logical Volume Group, a Physical Volume and Logical Volume Family and a Logical Volume.

With the UUID of the Logical Volume mount the LV:

Example:

    +-&gt; Logical Volume 9A7B21AA-F9FE-4E65-8C7E-ED2A73744C15
        ---------------------------------------------------
        Disk:                  disk17
        Status:                Online


Then use:

diskutil mount 9A7B21AA-F9FE-4E65-8C7E-ED2A73744C15


Then after getting the disk identifier of the mounted LV with diskutil list verify the volume:

diskutil verifyVolume disk17 # probably it's disk16, disk17 or disk18


If you get errors backup the data or the whole partition to an external volume then repair the volume with diskutil repairVolume disk17. 

One possibility to backup the data is dd. Attach a HFS+ formatted drive with at least 250 GB free space. Get the path to the external volume with ls /Volumes. Then unmount disk17 and disk0 with diskutil umountDisk disk17 and diskutil umountDisk disk0. 

Then clone the partition to a file: 

dd if=/dev/disk0s2 of=/Volumes/ExternalDriveName/disk0s2.rawdevice bs=4m


If the volume name contains spaces, escape the spaces with backslashes: ...of=/Volumes/ExternalDriveName\ With\ Spaces/disk0s2.rawdevice....

You can also use asr to restore the partition to another disk (as a temporary "backup"). Check man asr.