My favourit sport

I am fond of doing exercise, especially running. And I like to run alone on the side of road rather than the playground. l feel relaxed and comfortable after running. On the other hand In addition, I can keep healthy by running, which is the most important thing. So, I enjoy running.

1) Remember to put a space after a full stop.

2) playground - usually used for childrens who are under 10 years old play area, for adults you might say running track or field or exercise yard.

3) On the other hand - is used when making comparisons (eg. one good thing is this..... but on the other hand one bad thing is this...) However your sentences are about the benefits of running so you should use "in addition" or "furthermore". (eg. There is this good thing... and also in addition this good thing....)