You said 'back to dollar' which to me means you were able to purchase some bitcoins before using dollars, if that's the case you should be able to convert it back to dollar using the same method, whether it was an exchange or a service, etc.
OP said he want to convert his Bitcoin profit into cash using an exchanger,platform or something like that with lowest fees.
based on his statement alone we should understand that he knew how to convert it into Fiat and vice versa.
but the real question is where is the place with the lowest fee aka cheapest.
if you want to encash your Bitcoin profit into cash i recommend you to sell it to another Bitcoin users or peer to peer platform.
some people said localbitcoin is very high in fees,but you do not need to worry about it.
even though it's a bit big from others,in there you can raise the price a little bit and i am sure a lot of people raising their price to sell it in there.
which mean you do not need to pay the fees because you can raise the price in there and pay the price from that.
but the best way to encash your money is using 'Currency Exchanger' board in this forum.
if everything is right,you do not need to pay a fees for withdrawal and only need to pay the transaction fees.
find a trusted one and make a deal with him,so you do not need to spend some of your money for the fees and something like that