I forgot to include the followig sentences. I really hope you can have a look at them too.

1)How did Marlow consider Kurtz and why? Marlow considers Kurtz a hallow man because inside of him there was nothing to fight the influence of the wild jungle.
2) Why did the natives love Kurtz from the very beginning?
Because he came with the guns. The natives had never seen anything like that before.
3) Why did Kurtz fail according to Marlow?
4) How did Kurtz obtain ivory?
5) What did they do with Kurtz's ivory?
6) Who are the narrators and from which perspective do they tell the story?.Each narrator has his own perspective on events and characters, and some of them are deliberately deceptive in what they narrate.7
7)What does this narrative technique aim at? It aims at reaching the truth by selecting different accidents of the same event.
8) What does the impressionistic technique consist of?
9) What did Kurtz give Marlow before dying?
10) What were Kurtz's last words?
11) What lies did Kurtz tell Kurtz's fiancée?
12) What talents is Kurtz said to have (or have possessed)?
He is said to have been a musician, a painter, a journalist and a talker.

1. This is ambiguous: "How did Marlow consider Kurtz and why?"

It'd be better to write, "What did Marlow think of Kurtz and why?"

3. comma after "fail"

5. Who are "they"?

7. Delete "accidents" and insert "aspects" (word choice error).

11. Delete "Kurtz's" and insert "his own"

12. Change "to have" to "to have had" (verb tense should be past perfect).