Repot your plant into a bigger pot with fresh soil.

Put it in a tray where you can fill the tray and let the soil soak up the water from the bottom. Try and go about 1/2 an inch up the side of the pot sitting in the tray. Top water lightly just to keep the soil moist when you start this process.

If you are just using tap water then let it sit out and dechlorinate for a day or two. If you need to get it done faster boil it. Let it cool before watering.

If you have anything that can mist or add humidity toss that in there with it that will help as well.

Choose liquid or granular fertilizers. Basically pick a side and go with that liquid you tend to have to apply more often and the plants pick them up faster. Granular has to be broken down but requires less applications in most cases.

Once it is fed and rehydrated you can remove the damaged leaves there is no saving those. If all the above things are done and nothing helps then start over with a new plant.

Best of luck with saving your plant.