Q.My Christmas Cactus Is Dying What Can I Do To Save It?
What should I do? Possibly overwatering

Certified GKH Gardening Expert
If it is overwatering, then make sure to allow it to dry out, thoroughly. You may want to apply a fungicide as a preventative measure.
In the future, allow it to dry to the bottom of the pot between waterings. This plant prefers things on the dry side.
https://www.gardeningknowhow.com/ornamental/cacti-succulents/christmas-cactus
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm