wat is the different between 50 and 55 series??..i use myvi and i plan to get 195/50/15 or 195/55/15...
i currently using 205/45/16 and i can feel every bump on the road..my frens says change to smaller size rims and bigger profile tyre will solve my problem....

OK some simple maths time:
50 or 55 is the profile of tyre which denote the sidewall height
Example:
195/50/15=195 * .5(50% of 195mm for sidewall height)=97.5mm
195/55/15=195*.55=107.25mm
205/45/16=205*.45=92.25mm

so does it mean higher the sidewall, the more comfortable it will get cos it is depending if it is soft compound or hard compound tyres?

And in general, the higher/thicker the sidewall, the more comfortable it usually is (it's like your sitting in chair a thin cushion vs one on thicker cushion).
For your case, the best is to downgrade to 195/55/R15 as it will give you the most comfort and still retain about the same overall diameter as your current 205/45/R16.