What can really reduce the size of the prostate so that one can urinate well without impediment ?

The only certain way of reducing the size of the prostate is with surgery.

However, apart from the obvious need for an anaesthetic and general discomfort, there are also complications associated with this such as erectile dysfunction.

Prescribed medication such as tamsulosin and finasteride can help, as well as Saw palmetto, but their effects are not guaranteed.

However, we also know that the size of the prostate does not necessarily determine the degree of symptoms, so you might wish to try oral medication to see how you respond before resorting to surgery.