The other onnes can grow back

Is that where it normally sits? In an office with no light?

First, it needs light. If you can't put it in outdoor shade, put it as close to a window as possible.

Secondly, remove all of those dead trunks. They most certainly will not grow back. They are decomposing in the pot and creating rotten conditions. That's fine in a south American wetland, but not in a container.

When you remove the dead trunks, you'll want to re-pot the live trunk in a mix that is porous and free-draining - a mix that can be thoroughly flooded and then drained well. This will help avoid root-rot during the Winter.

Two weeks after the re-pot and re-location, you'll want to begin fertilizing the plant.

Josh