靠近边境一带居住的人中有一个精通占卜的老人，Near the border lived a man who is well versed in divination. 他们家的马无缘无故跑到了胡人的住地。His family horse ran off to the Hu area.人们都前来慰问他。His neighbors/friends came to console him. 那个老人说：“你怎么知道这不是一件好事呢？” The old man replied, "How do you know that this is not a good thing?" 过了几个月，After a few months, 那匹马带着胡人的良马回来了。That horse came back with several good horses from the Hu area. 人们都前来祝贺他们一家。His neighbors came to congratulate him. 那个老人说：“你怎么知道这不是一件坏事呢？” The old man replied, "How do you know that this is not a bad thing?" 自此，From then, 他家中有了很多好马，his family has many fine horses. 他的儿子喜欢骑马，His son loves to ride horses. 结果从马上掉下来摔得大腿骨折。This resulted him from falling off one and broke his thigh bone. 人们都前来安慰他们一家。People came to console . 那个老人说：“你怎么知道这不是一件好事呢？” The old man replied, "How do you know this is not a good thing?" 过了一年，A year later, 胡人大举入侵边境一带，The Hu barbarians led a great invasion to the surrounding borders. 靠近边境一带的壮年男子都拿起弓箭去作战。All the men from the surroundinging areas took up arms. 绝大部分都死了。Many were killed. 唯独这个人因为腿瘸的缘故免于征战，Only because of the lamness, the son was not conscripted. 父子得以保全生命。Father and son were able to survive.
I shall correct your English without looking at your Chinese. The 2nd one will be my translation :)
Chinese Idiom Story 塞翁失马焉知非福Once upon a time, there was an old man who lived near the border and was well versed in divination. One day their his horse accidentally fled ran off to the Hu (a northern barbarian tribe) side. People Those who knew him, came to comfort him. However, the old man said: "How do you know this mustn't won't be a good thing?" After a few months, the horse came back with lots many other fine horses of from Hu. People Again his fellowmen came and to congratulate himtheir family. Once more the old man said: "How do you know this mustn't won't be a bad thing?" Since then, As they now have many had a lot of good horses, and that his son likes to ride them, horseback riding, which resulted in falling from the horse He fell and broke his leg thigh. People came to comfort the old man but he him. The old man said: "How do you know this mustn't won't be a good thing?"