how does currency fluctuation affect the economy of a country?

A lot. It does affect the import and export of a country, which is basically the main source of income

Not greatly - the fluctuations are usually quite small and fast. HUGE fluctuations would reflect real bad damage to an economy - and then the economy would certainly be changed.

it effects in such a way . when indian currency falls in respect to dollar that is 1 dollar become 55 Rs instead of 50 rs,

for all the imports india has to pay more as if you buy crude oil for 1000 dollars instead of buying it at 50,000 rupees india will buy it at 55000 rupees , this means now as crude oil has come at higher cost rate of petrol will rise and transportation cost will increase , as transportation rate increases and in such way price of things and vegetables will also rise.

this way currency fluctuation affect economy