Q.calla lily
I have a calla lily in a pot indoors and the flowers are turning brown on the outer edges.what should I do

That's normally what follows the flowers turning green, and it means the plant is entering a dormant stage. If yours didn't turn green first, another possible cause could be that the edges of the flowers are getting sunburnt from too much direct light (if you're in a warmer climate). Keep in mind even though the plant might be indoors, glass magnifies the heat.
These articles may help you:
https://www.gardeningknowhow.com/ornamental/bulbs/calla-lily/green-calla-lily-blooms.htm
https://www.gardeningknowhow.com/ornamental/bulbs/calla-lily/deadheading-calla-lily-plants.htm