Most exchanges have conversion to usd and vice versa Just check the major ones like Yobit or Cryptopia. Whatever should suit you though
We are facing hard times in crypto market and in this situation making profit is not so easy. You must wait for some time when the market turns from red to green. The problem is that when the price falls more and more people demand for bitcoin and when the price grows more traders cannot find buyers in the market. To whom they would sell their coins for higher price.