Some people ride 9 bar. But 7 bar or 8 bar should be ok in the beginning. It also depends on you weight...
What do you mean your brakes are not sharp? The braking power is too low? I assume you have a u-brake for both wheels, right? What kind of rims do you have? Black anodised, painted (mainly to be found at coloured rims) or chrome? This makes a difference...
You can try those clear brake pads like Baradine or similar. They are very soft and grippy. The disadvantage is that you can not brake only a little bit so easy anymore. You brake or you don't. But if you want higher maximum brake power you should try them. But expect them to squeak!