The previous part is below

Mon rêve effrayant mais drôle

Le patron avac sa hache. Sailor Moon qui ne pouvait pas jeter un sort.
I'm sure to understand quite well. Maybe you mean that as long as the boss had his weapon you couldn't cast a spell, in this case, you would say "Tant que le patron avait sa hache, Sailor Moon ne pouvait pas jeter un sort."

La équipe de tueurs professionels qui avait peur de la Sailor Moon sans défense.
There is no need of "qui" here, nor "la" in front this proper noun.
L'équipe de tueurs professionnels avait peur de Sailor Moon sans défense.

Je crois que mon réve était effrayant mais drôle !
This one is almost perfect. Also, instead of "je crois" you can use "trouver" at "passé composé" "j'ai trouvé". It has not the classical meaning of finding something, but the same as "croire" in this case.
Je crois que mon rêve était effrayant mais drôle !

That's great, you are writing more complex sentences and you are making great progress :D

Hope this helps ! :)

This is the end. This is WAY too long ^^ sorry, I will try to be more concise next time. Sorry, I lost the color when copying/pasting.

Mon rêve effrayant mais drôle

Je suis allée à la bibliothèque pour lire des livres à propos des centrales nucléaires. Le contenu de les des livres étaitent effrayant ! Des gens qui ont perdu leurs familles à cause des radiations et de la maladie... Ces mots m’ont rendus triste.

Après je suis revenue à la maison, j’ai lu un article sur un gars adolescent qui a tué sa camrade de classe féminin (avec un couteau en morceaux)/en la coupant en morceaux. J’ai été choquée par la historie l'histoire.

Après un moment, j’ai fait une sieste. Dans mon rêve, il y avait une équipe de tueurs qui avaient envisager de me tuer. J’ai finalement rencontré le patron de l'équipe féminine qui a essayé de me tuer avec sa hache.

Je me sentais que c’était vraiment dangereux... et j’ai me je me suis transformée en Sailor Moon ! Je ne pouvais pas jeter un sort. J’étais juste s’enfuir Je pouvais juste m'enfuir. Mais il semblait que mes enemies pouvaient se sentir ‘une aura différente’ autour de moi XD Et je me suis enfuis d'eux sans problème.

Le patron avec sa hache, Sailor Moon qui ne pouvait pas jeter un sort, l'équipe de tueurs professionels qui avait peur de la Sailor Moon sans défense, je crois que mon rêve était effrayant mais drôle !

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J’étais juste s’enfuir.
The verb is "s'enfuir" you don't need to use "être" : "Je m'enfuyais juste" (imparfait). If you want to mean that you could only run away you would say "Je ne pouvais que m'enfuir" which more natural in french. "que" is the sentence shows that this is the only thing you can do.

Mais il semblait que mes enemies pourraient se sentir ‘une aura différente’ autour de moi XD
I don't understand quite well what you meant here, but here a correction :
"ils pourraient" is conjugated at "conditionnel", it doesn't fit here, it has the sense of "could/might". Use imparfait instead, (action that lasts happening in the past)
Mais il me semblait que mes ennemies pouvaient sentir ‘une aura différente’ autour de moi XD

Et je me suis enfuie de leur sans probléme.
In french, you can't really precise the person you are running away from when using "s'enfuir". To correct, you can simply remove "de leur" : "Et je me suis enfuie sans problème." If you still want to precise the person you would use the verb "s'échapper" combined with the expression "l'emprise de" = "the fact of being taken" : "Et je me suis échappée de leur emprise sans problème."

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J’ai finalement recontré le patron de la équipe féminin que a essayé de me tuer avec sa hache.
That one is also almost perfect, "la" + word starting by a vowel gives "l' ". "équipe" is feminine so you have to add an "e" to "féminin". You would not use "que" here but "qui" because you want to use the object of the first clause "patron" as the subject of the second one.
J’ai finalement rencontré le patron de l'équipe féminine qui a essayé de me tuer avec sa hache.
Je me sentais que c’était vraiment dangereux...
There is no "me" here because your feeling is about the situation itself. If the feeling is about you, like in "je me sens bien" (I feel good) you use a "me".
Je sentais que c’était vraiment dangereux...

et j’ai me transformée en Sailor Moon !
"transformer" has the auxiliary "être".
et je me suis transformée en Sailor Moon !

Je ne pouvais pas jeter un sort.
Perfect !

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Hi Jinsil!

Mon rêve effrayant mais drôle

This sentence is perfect.

Je suis allée au la bibliothéque à lire les livres de la centrale nucléaire.

You wouldn't use "au" but "à". "au" is actually used where you would say "à le", but "à le" is never used, it just a way to know when use "au". "bibliothèque" is a feminine noun, so in this case you would say "à la bibliothèque". Notice also the different accent. There is also no "à", you say "aller" + infinitive verb, exemple : "aller manger", "aller dormir", "aller lire"... You wouldn't use "les" here because if you are talking about books in general, you would use "des". You cannot also use "de" here. "de" in french is used to tell that something belongs to someone. "le livre de Jean" = "Jean's book". You are saying that the books are belonging to the nuclear plant here ^^. If you want to say that the books are about the nuclear field, use "à propros" ou "parlant de". I removed the last "la" because it is the same as "les/des". I guess these books are not about a particular "nuclear plant" but nuclear plants in general.

Je suis allée à la bibliothèque lire des livres parlant de centrale nucléaire.

Le contenu de les livres étaient effrayant !

You have to make "de les" one word "des". That one is difficult : the subject is "contenu", it is singular, so the verb "être" has to agree with the subject ("était"). You didn't make the mistake of adding an "s" to "effrayant" Bravo! "effrayant" also agrees with the subject "contenu" which singular thus there is no "s" at the end of "effrayant". 

Le contenu des livres était effrayant !

Gens qui perdu leurs families à cause de La radiation et maladie... Ces mots m’a rendu triste.

In french unlike in english, always place an article in front of "gens". You can't use "qui" here. It would be used if you want to make the object of a first clause the subject of a second clause. Example :

Je connais des gens. (first clause, "gens" is the object of the verb)

Les gens sont heureux. (second clause, "gens" is the subject in this one)

If you want to connect these two sentences, making "gens" object of the first clause and at the same time subject of the second clause you would "qui" :

Je connais des gens qui sont heureux.

That is the case here, so there shouldn't be any "qui".

You also have to conjugate "perdre", "perdu" is just a "participé passé", place an auxiliary, "avoir" in this case in front of it ("ont perdu").

When talking about "raditions" it is generally used at a plural form, instead of "la", you would use "des". You also have to place again "de" after "et" because you used "à cause de", and the article "la" in front of "maladie".

Des gens ont perdu leurs familles à cause des radiations et de la maladie...

Aprés je suis revenue à la maison, j’ai lu un article de un gars adolescent qui tua sa camrade de classe féminin avec un couteau en morceaux.

This one is almost perfect, and this article is terrible indeed. "Après" is written this way. "de un" is contracted -> "d'un". "gars adolescent" is correct, in this case "adolescent" is an adjective, you can also use "adolescent" as a noun. "tua" is grammatically correct, it is conjugated at "passé simple" but it very litteral and it is used for an action that lasts which doesn't fit here, prefer "a tué" ("passé composé"). A "e" is missing a the end of "féminin", it is an adjective and you have to make it agree with "camarade" which feminine in this case. (The masculine and the feminine form of "camarade" is written the same way). You can't use directly "en morceaux", you have to use an verb like "couper", (cut) at the "participe présent form" for example : "en la coupant en morceaux" "la" is referring to the "camarade". "en" indicates how this action is performed. It is the equivalent of by vb-ing in english.

Après je suis revenue à la maison, j’ai lu un article d'un adolescent qui a tué sa camarade de classe féminine avec un couteau en la coupant en morceaux.

Après je suis revenue à la maison, j’ai lu un article parlant d'un adolescent qui a tué sa camarade de classe féminine avec un couteau en la coupant en morceaux.

This is an alternate version which is better using "en parlant" like in one of the first sentence.

J’ai été choquée par la historie.

This is almost perfect. "h" is never pronounced in french, it sounds like "la (h)istoire" so you have to contract the two words "l'histoire". Also, the "i" is just before the "r".

J’ai été choquée par l'histoire.

Aprés un moment, j’ai fait une sieste.

Apart from the accent, this is perfect. "Ensuite" instead of "après un moment" is more natural in this case, but you sentence is still very correct.

Ensuite, j’ai fait une sieste.

Dans mon réve, il y avait une équipe de tueurs qui ont envisager de me tuer.

You are using the verb "envisager" at "passé composé", so you have to conjugate the "participe passé" "envisagé". Also the subject is "équipe" which is singular, so you would use the auxiliary "avoir" at a singular form "a"

Dans mon rêve, il y avait une équipe de tueurs qui a envisagé de me tuer.

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