Yikes. Not sure what the problem is, but I would definitely chop and prop cut off the pieces that look healthy. Let it callous over for a day or two and then put it up in a succulent mix.
You know I never had luck with this one.I heard they are fussy with the water so dont use tap.I didnt listen &mine looked like it was crystallized after watering a few times smh.๐ฅHopefully you have better luck with yours.They are such a cool plant.๐