How i can increase my sex time? and is it safe using viagra (sildenafil)

?: Not sure what you mean by increase your sex time. If referring to premature ejaculation, that should be discussed with a qualified doctor locally. It can be due to either psychological or, less likely, physical issues. About viagra, (sildenafil) you should not use it unless you have erectile dysfunction. It has side effects, primarily with the heart if you have underlying disease or predisposition for it.