I'm lost as to your hair being stiff. What do you mean by that? If it's somewhat long you may just be needing a good haircut. I would recommend going to a reputable beautician and see what they have to say. They should be able to answer your questions and help solve your problem.
I see. You have more like coarse, thick hair. I would try deep conditioning and products to help give your hair a sleeker look. I recently tried Suave's sleek line, the creme you put in your hair before drying. I thought it worked as well as the creme I pay 5 x's more for at the salon! For a couple bucks it's worth a try. Good luck. And as I mentioned before, a beautician should be able to offer advice as well.