I don't know if I 'm the only one who hates running so much and is so bad at it.

Conjugation = who hates, who is

When I was a kid, I'm was afraid to go to PE class because of the running routines.

I was = past tense

I guess that why I took swimming class rather than running when I went to college.

I don't know if any other countries have the same rules , but in China, we have a running test as a part of the final exam for each semesters in college.

They actually ask you to run a 1000m and record your result.

If you can't finish the run within certain time range - 4 mins 30 seconds for boys and 4 mins 32 seconds for girls, - then you won't be eligible for scholarships or distinction.

Someone told me that I need to change themy rhythm and adjust myour breathing when youI running.

I need to change my rhythm and adjust my breathing when I run --> if talking about yourself specifically

You need to change your rhythm and adjust your breathing when you run --> if talking generally

Well, it's not easy to think about any skills when you are out of breath.

There are no errors in this sentence, but I also wrote a more natural version --> Well, it's not that easy to think about your technique when you're out of breath.

Imaging that you are dragging your sore swollen legs and that every time when you breathe you can taste the rusty blood in your mouth.

LIt may looks like you're running, but I bet walking is even fast than thatwould be faster at the moment.

I have the greatest respect for anyone who enjoys running.

Conjugation = who enjoys

And I was thinking that maybe my attitude towards running is similar to my attitude towards my marriage.

I always know that there' are some certain things that I hate and that I can't do it or I'm not good at it, so when every time itone shows up, I will directly surrender in my subconsciousnessimmediately subconsciously surrender.

"There're" is not a typical contraction that I've seen. You could probably still use it, but I think it would very informal, eg. when texting a friend.

Things that I hate and things that I'm not good at.

No need to use "it" as you've already used "things".

Things is plural, so pair it with "one" (as in one of several things) rather than "it" (one single thing).

I removed "will" as it sounds like the sentence is talking more generally, rather than about a specific future event.
Examples
General --> When it rains, I always stay home. Every time I encounter a spider, I run away. When I'm tired, I have a nap.
versus
Future --> If it rains today, I will stay home. If I encounter a spider while I'm camping this week, I will run away. When I get tired tonight, I will go straight to bed.