Penis exercises don't really exist. The reason is: There are no muscles in the shaft of your penis.
Please: Don't try to save a few dollars on a high quality traction device, use jelqing, penile “exercises” or any other free hand pulling, and risk.
Using curved penis exercises is one possible way on how to straighten a problematic or severe curved penis caused either by your genetic material or Peyronie's disease. I will distinguish between naturally curved penis (caused by genetics) and penile curvature caused by Peyronie's.