Yesterday I saw a documentary called (1) "The Spirit of the Marathon" and, as(2) its(3) title says/suggests/indicates (4), is about the runners who(5) have run a marathon. <...>

In the documentary, several people spoke (6) explaining what their goals were (7), why they wanted to run a marathon. One (8) girl wanted to run a marathon after she had had a bad personal experience (9), she had divorced and she had gained weight and she had fallen depressed, then she began training for a marathon. (8) Another girl (10) was a runner and she wanted to run a marathon to raise funds for the orphanage (11) where she had been adopted. The third girl was a professional athlete (12)but she had had a injured ligament so in this time she was training for running again a marathon.(13)

Another (10) runner was (14) a boy from Kenya (15) but he lived and worked in Japan. He was training to (16) win the marathon because in the past (17) he had been the third and the second so he wanted in this marathon to be the first. Finally there was a marvelous (15) man that was retired and he had run several marathons and in this marathon he wanted to improve (18) his time to finished the race, he said that he liked running (the) marathon between others reasons was why not everyone could run a marathon. (19) They all will run Chicago's Marathon. A marathon is a mentally challenge and a physical challenge (20) <...>

1. La palabra "titled" funciona aquí, pero se dice "called" mâs frecuentamenta. 

2. Se usa "as" para describir algo que pensaría. "Por supuesto", el atlético corre más rápidamente que el gordo = "the athletic man ran faster than the fat man, as expected" 

3. its = "su", it's = "es" 

4. Estas palabras son mejores en esta frase. Se puede usar cualquiera (indicates, suggests, says), pero pon atención a la última letra "s". 

5. Como "los que han corrido", necesitas la palabra "who"

6. En inglés, los verbos siguen los sujectos casi siempre.

7. Usar "which" es raro en inglés. Normalmente, se dice "what". Es por eso que muchos americanos preguntan "¿Qué color, día, trabajo?" en lugar de "Cuál <>?"

8.Gramática

9. Bien hecho. Usaste este tense muy bien. 

10. "Other" es adjectivo. "Another" es una persona o una cosa. Es una palabra "combinada" (no creo que sea como se dice) "an + other", como "a + el = al" en español. 

11. "orphan" es la persona. "orphange" es el lugar en que viven.

12.  Se faltan letras

13. No entiendo, pero he visto la película. Te recomiendo: "and had to modify her training for this marathon". 

14. "was from" en lugar de "came from"

15. letras

16. "for a race" o "for a personal best", pero "to win"

17. "in the past" no "in the previous" 

18. Ya es pasado porque "wanted". "Wanted to improve" = "quería mejorar". "wanted to improved" sería "quería mejorada". 

19. Intentas decir "el gustaba correr el maratón porque alguien puede hacerlo"? Si sí, usa "he said that he liked running the marathon because, among other reasons, anyone could do it". 

20. Opciones: "a challenge, both mentally and physically", "a mental challenge and a physical challenge"

21. Ya es cierto, pero sería mejor decir: "I hope to run a marathon sometime in my life"

Yo también corre. He corrido dos maratones, pero prefiero las distancias más cortas, como el 10K. Me gustaría hablar más contigo de nuestras carreras y entrenamiento. 

The Spirit of the Marathon

There's some good writing here. I would say the most important thing you need to work on is punctuation. You are joining many separate sentences with commas, which makes it very awkward to read. Try to make your sentences shorter. It's a difficult topic to teach, and really comes with experience as much as anything.

The Spirit of the Marathon