I have a certain amount on which I have already given khums last year. I still have that savings with me so is khums applicable on it or not? For example; I have 50000RS from which 10000 is from last year and I have already given a khums on it. So for now how much I will consider for khums?

Only if you have more than 40,000 RS, the you need to pay the khoms of the excess.