As we all know, life lies in movement. My favourite sport is running. Because (改：because) it can keep me healthy and relax my mind after busy study.（段评：本段作为开头,点明了运动的重要性并引出了自己最喜欢的运动,表达清晰！但存在两个需要改进的地方: 1. 句式结构:'Because it can keep me healthy...'是一个不完整的句子,应与前一句合并或改为完整句。 2. 词汇表达:'relax my mind'可以用更地道的表达'help me relax'来替代。修改版：As we all know,life lies in movement. My favourite sport is running,because it can keep me healthy and help me relax after busy study.）

Last week I took part in a running race. It was a special experience. Though I didn't win, I kept running to the end.（段评：本段描述了一次跑步比赛的经历,内容具体！但可以通过添加细节让经历更生动: 1. 缺乏细节:可以加入比赛时的感受或周围环境的描写,如'When I felt tired,I heard my classmates cheering for me'。 2. 句式可以更丰富:使用'Although...'引导的让步状语从句替代'Though...',保持句式多样性。修改版：Last week I took part in a running race at our school. It was a special experience for me. Although I didn't win the race,I kept running to the end with the support of my classmates.）

From running, I learn (改：have learned) to be fit and never give up. Sport bring (改：brings) us health and happy (改：happiness) .（段评：本段总结了跑步带来的收获,主题明确！但存在两个语法错误: 1. 主谓不一致:'Sport bring'应改为'Sports bring'(主语是复数形式)。 2. 词性错误:'happy'是形容词,应改为名词'happiness'(作动词bring的宾语)。 同时,可以用'learned'替代'learn',保持时态一致(描述过去的经历)。修改版：From this running experience,I learned to keep fit and never give up. Sports bring us health and happiness.）

Let's do sport together.（段评：本段作为结尾,发出了呼吁,简洁有力！可以通过添加鼓励性的表达让结尾更有感染力,如'Let's do sports together and make our lives more colorful!'。修改版：Let's do sports together and make our lives more colorful!）