If there are 5 sharps in the key signature, they are F, C, G, D, and A. You could lower it 1/2 step and play in the key of B flat. But my guess is that if you play just the first 4 measures in the written key, you could get the feel of reaching for those sharps.
A piano teacher might suggest that you practice Right Hand and Left Hand separately and then put them together. All of the notes are black keys except B and E. Good luck. It's like any skill you practice--FMQ or playing sharps. The more you do it, the better you get.