Today, when I am going shopping with my friends, we decide to buy the product that is on sale. If we are lucky, we can gain the prize.

Today, when I am going shopping with my friends, we decide to buy the product that is on sale. If we are lucky, we can gain the prize. We believe that none of us have such luck. When we pay the bill and check out the number, we are so surprised that we win the small prize. What a lucky day. 
我今天和朋友逛街的时候我们打算去买打折的东西。如果幸运的话，还可以获得奖品。我们都觉得我们不会有这样的好运气。不过我们付完钱后，查看了数字，我们都惊讶了，因为我们得了一个小奖。好幸运的一天啊。