Not a fern by a long shot. It's either Monstera obliqua or Monstera adansonii. They're aroids, not ferns. I'd lean towards it being the M. adansonii, the M. obliqua leaf is a little different..

They like a lot of light but look better if they're not in direct sun all the time. Possibly the problem with yours is too much water. Either the soil not draining well, or the roots having blocked the drain holes and not letting water escape. Best to check that first.