英语翻译中文部分：很多朋友尤其是亲戚长辈不理解我为什么要掏钱去健身房跑步,而不直接在户外免费的跑步.我个人觉得原因有三：

英语翻译
中文部分：
很多朋友尤其是亲戚长辈不理解我为什么要掏钱去健身房跑步,而不直接在户外免费的跑步.
我个人觉得原因有三：
1.不受干扰：其实上海的街道是不适合跑步的,路上的红绿灯,行人,机动车都会或多或少是一种干扰.
2.不受天气影响：你不用管天气是刮风还是下雨,只需要换好衣服,站上去就跑；同时,健身房里的温度也不会太冷或太热,可以让人在一个很舒适的环境下奔跑.
3.能精确计算数据：只需扫一眼面板,你就会知道自己以每小时几公里的速度跑步、已经跑了几公里、运动了几分钟,不必可以的统计数据,也不必特意的控制速度.
英文部分：
Some of my friends especially eldership doesn’t understand why I pay money that running at gym and don't just run outside for free.
My opinion is:
1.Distraction-free:Shanghai Street actually is not fit for running.The traffic lights,passers or vehicles are always disturbing you when you are running.
2.Don't need care weather:Whatever strong wind or heavy rain,you just need changing your coat,standing on the machine then running.In another hand,the temperature would not be cold or hot,let you running under a comfortable circumstance.
3.Get the correct data:you can see everything in the dashboard by the machine.The calorie,distance,time,incline,speed,heart rate and etc.Don't need calculate data deliberately,and don't need control speed when you're running.
PS,中文部分知识想要表达的大意.需要修改的是英文部分明显的错误以及将英文部分改得通顺些,不必完全按照中文翻!

Some of my friends and relatives, especially the elders, couldn’t understand why I pay for running in gym rather than just running outdoor for free.
Three crucial reasons account for my choice.
1. Compared with running outdoors, running in a gym has less disturbances. Basically, Shanghai Streets are not ideal places for running. Oftentimes, you will be disturbed by the traffic lights, pedestrians or vehicles, when you are running in the street. This will absolutely ruin your good moods of doing exercise.
2. Bad weather will not be a problem anymore if you are running in gym. Protected by the gym, you do not need to worry about bad weathers. No matter what wheather it is , the moment you want to exercise, all you need is standing on the gym running machine. Furthermore, the temperature in a gym can be controled, if you want, it will never be too cold or too hot. I enjoy running under such a comfortable circumstance.
3.With the aid of equipments in gyms, you can exercise more wisely. Gym running machines have various functions. They can not only show you informations on how many calorie you burn, but also the distance you run, your running speed, heart rate and etc. According to these data, you can adjust your exercise schedule correspondingly to get a better result.

To sum up, for the reasons above, I prefer to run in a gym than outdoor when I can afford to it.