Recently, I am reading an erotic an article.

I don’t know what you are trying to say here. Erotic means explicitly/graphically sexual.

The man actor runs everyday, so he is in good body shape.

And there is a girl always goes running, sone girl runs also. She looks good, too.

In recent years I ran occasionally recent years.

I like swimming mostre.

You could also say “I like swimming the most”

Since I live in a small town without a swimming pool, and it's too inconvenient to go to the pool, so I decided to run again.

Once I ran 3 km at least 3 km.

But I hadn'r t run for a long time, so even 2 km was even a little hard for me.

I asked a friend, who loves running and is wild about running marathons to run with me.

Because I was afraid that I could'nt fininsh my 2km-running alone, Iand needed someone to guide me.

Marathoning was popular a few years ago, especially among the white collars and the enterprise workers and entrepreneurs.

I sighed up a game for a 5km-running race once, but I was too busy to attendgo.

Attend is usually used for classes.

From then on, I never registered any moregain.

There was also a book popular inat the same time, which was written by the Japanese author Murakami Haruki.

I haven't finished reading the book forin a long time.

Recently, I am've been reading an erotic article.

The main actor runs everyday, so he is in good body shape.

And tThere is also a girl who always goes running, s. She looks good, too.

I know there are many advantages tof running,. I don't like it, but I don't hate it either.

I ran occasionally in recent years.

But I like swimming most.

Since I live in a small town without a swimming pool, and it's too inconvenient to go to the pool, so II have decided to runtry running again.

OncThere was one time I ran 3 km at least.

But I hadn'rt ruan for a long time, so even 2 km was even a little hard for me.

I asked a friend, who loves running and is wild about convincing me to run a marathon to run with meher.

Because I was afraid that I could'n't fininsh my 2km- running alone, I needed someone to guide me.

MRunning marathons was popular a few years ago, especially among the white collars and the enterpriseworks and entrepreneurs.

I sighned up a game for a 5km- running once, but unfortunately I was too busy to attend.

From then on, I never registerded for another run any more.

There was also a book popular during the same time, which was written by the Japanese author Murakami Haruki.

ItsThe name is " What am I thinking about when I am running".

I haven't finished reading the book again for a long time.

Recently, I am reading an erotic article.

Grammatically this is fine, but I'm not sure if "erotic" is really what you want? This means that you're reading a very sexual article, an article intended to make the reader sexually excited. If that is what you mean, in English we'd probably call it a "romance novel" or a "romantic serial", something like that - we're shy :)

The manle actor runs every day, so he is in good body shape.

"man actor" is okay but sounds a bit awkward.

And there is a girl who always goes running, she looks good, too.

I know there are many advantages of running, but I don't like it, but. Although I don't hate it either.

"although" is just another way of saying "but" so that you don't have to repeat yourself. You needed a conjunction between the first two ideas, they contrast too much to simply use a comma.

I ran occasionally in recent years.

More natural: "I've run occasionally in the past few years."

Since I live in a small town without a swimming pool, and it's too inconvenient to go to the pool, so II've decided to run again.

"Since" and "so" were both doing the same thing - each of them is in the correct place for the correct reason, but you only need one of them.

Simple present tense isn't good here. You could've used simple past "I decided", but present perfect "I have decided" is most natural, because it's a past decision with present consequences. In the past, you decided, but because of that past decision, you are presently in a routine of going running.

But I hadn'rt run for a long time, even 2 km was even a little hard for me.

It sounds better this way round, but I'm not sure exactly why.

I asked a friend, who loves running and is wild about marathons, to run with me.

This would actually work without any commas at all, but once you started off the parenthetic clause with the first comma, you needed another comma to finish it before continuing the sentence.

Because I was afraid that I could'n't fininsh my 2 km- running alone, I needed someone to guide me.

could not -> couldnot -> couldn't

Marathon running was popular a few years ago, especially among the white collars and the enterprise workers and entrepeneurs.

Or "Marathons were". Singular "marathon" almost always refers to a single marathon event. He ran a marathon yesterday. They will be having a marathon in town next weekend.

I sighned up a game for a 5 km- running competition once, but I was too busy to attend.

From then on, I never registered any more.

More natural: "I never registered again".

There was also a book popular inat the same time, which was written by the Japanese author Murakami Haruki.

The English convention is to say Haruki Murakami. Of course this isn't wrong, but just to note :)

"in" is okay but "at" sounds much better here.

Its name is " What am I tI Am Thinking aAbout wWhen I aAm rRunning".

Convention is to capitalise the first letter of each word in a book title. "What am I thinking about" is the word order for asking questions.

This may just be a quirk of translation, but English sources give the title as "What I Talk About When I Talk About Running" :)

I haven't finished reading the book for a long time.

"I haven't finished reading it" is what you would say if you *are currently* reading it, but you have not finished yet. Or if you gave up, and never finished.

Well, I was thinking about "what I am I thinking about when I am running."

You should probably do title capitalisation here too, but I'd say it's up to you :)