How much is it?

얼마예요? has the same frame as day 4's 이게 뭐예요?: a question word followed by 'is', and the answer drops the price into the same slot. Prices are always Sino-Korean, day 8's set, because money is measured rather than counted item by item. 원 ends in a consonant, so every price you hear ends in 원이에요, whatever the number. That gives you a fixed landmark at the end of the sentence while you are still working out the figure.

English groups big numbers in threes, thousands and then millions, and the commas follow suit. Korean groups them in fours, and 만, ten thousand, is the unit it builds on: 50,000 is 오만, five 만, and 100,000 is 십만 (simman), ten 만. The trick for reading a price is to move the comma one place to the left in your head, so 50,000 becomes 5,0000 and the 5 is the number of 만. Expect this to feel slow for weeks, because English habit keeps splitting the number at the thousand.

좀 깎아 주세요 is the 주세요 pattern from day 6: 'cut it down a little for me'. 깎다 means to pare or shave, as you would an apple, and bargaining is pictured as paring the price. 좀 softens the whole request, like just or a bit, and without it the sentence sounds like an order. 카드 돼요? uses 되다, a verb meaning to become or to work, so rather than asking permission you ask whether card works here, which is how Koreans ask about almost any service.