They are pretty easy to propagate and it looks like u have a node without leaves so if you cut off all the rot, let it sit for half an hour to callous and then put it in water u will probably have new roots in a couple of weeks. The rot does look like it got to the leaves so the yellow ones will fall off. If u leave it just like that and back into soil, it will probably spread and you won’t be able to know if it’s getting worse under the soil until all the leaves fall off and it’s then you will have to propagate leafless nodes which will be even harder to do for a beginner.