Just got this cactus from my father, he just left it in a the pot it came in and it retained too much moisture.

I also believe that it was buried too low hence the browning.

The root(s) have fallen apart but there is no rot. Some of the tubers(?) were soft and were removed) but the ones near the top are still firm.

I'm wondering
> How deep should I plant it
>What potting mix would you recommend? I live in FL and it rains alot

I'm going to let it dry and place it in equal parts lava rock, pebbles and soil.

Thank you.
Also this is a general help thread.