No idea about the moss, but, well, Stromanthes are one of those plants that a lot of people find hard to keep alive. I personally won't even attempt them. Some people will no doubt post that I'm being excessively negative. But if you "have no idea with plants," well. Don't get real attached.

Nevertheless, let's try:

The big key is water. Don't let the plant dry out (like, water when the top half-inch of soil is dry, give or take), and -- the more difficult part -- they need high humidity. Pretty much all the time. Which is probably what's wrong with yours; it's reacting to the dry indoor air. Calatheas and Marantas (other plants in the same family) will do the same thing.

There are varying schools of thought on how to increase humidity levels. Sometimes this leads to arguing. I don't want to start anything, but:

Some people say you can get a misting bottle and just spray water at and around the plant at various times during the day. The problem with this is that it may or may not (there's where the argument comes in) actually raise the humidity levels more than about five minutes at a time. I think it's probably better than nothing, and for plants that appreciate moist air but don't *need* it, it's nice to do sometimes, but I don't think it's the answer here.

Another school of thought involves the use of "pebble trays," which are more or less what they sound like: trays. With pebbles in them. If you keep water in the tray, and have it near, or under, the plant, then the water evaporating off the tray raises the local humidity level. The down side is that there's disagreement about whether this provides enough of a long-term increase to be worth bothering with. There's also a danger of drowning the plant: if the soil touches the water, the water can be drawn up into the soil. With a Stromanthe, that might not be such a terrible thing, but even so, I wouldn't recommend putting the plant *on* the tray. Maybe tray-adjacent, if you bother with one at all.

So, what to do?

If it was me, I would be inclined to discard the plant and start over with something a little less bothersome. But if there was, like, a $1 million prize for keeping it alive for a year, I would. . . .

Put it in a terrarium, a clear plastic box of some kind, something that could be opened and closed easily to tend the plant, pick off old leaves, etc., but would keep humidity and water levels steady. Maybe a garage sale aquarium, or something like that. This isn't foolproof -- you would have to watch for rot, when you first set it up, and then after it's established you have to make sure not to let it sit in sun at all, or it'll cook to death. But it's a lot easier than sitting next to it, misting every fifteen minutes.

Alternately, you could try keeping it in a bathroom, if you have or can get reasonably strong light in your bathroom on a steady basis. Though that depends on what your heating and air conditioning situation is like in the bathroom.

I'm sorry I can't be more encouraging about this. We have optimists around, somewhere, though; maybe one will come by.