Thank you very much for your corrections. Here are some more sentences on the same theme I'm not sure of.
1)The narrator can be a first-person narrator, who/which (?) uses the first-person voice .
2)He can be used to bring the reader close to the feelings of the narrator, to convey an impression of reality and to restrict the reader’s point of view.
3)A character is a person present (?)/represented in a story. As for the characters, they could be flat characters, when they have a single psychological trait.(better: Characters can/may? be divided into flat and round. The former are built on a single psychological trait, whereas the latter change their personality during the action).
3)The characters could (better: can, may?) be presented in two different ways, that is (namely?) directly and indirectly. When the presentation is direct, the character himself talks about himself.
4)Characters can be major or minor. A further distinction should/can (?) be made between flat and round characters.
5)The functions of the first-person narrator are as follows./ A first-person narrator can have the following functions. First, it has the function of conveying (it/he conveys?) an impression of reality,
of restricting the reader’s point of view and finally, of bringing the reader close to the feelings of the narrator.
6)Join the various types of characters using appropriate linkers, such a as “a first distinction can be made between flat and round characters”.
1) The narrator can be a first-person narrator, who/which (?) uses the first-person voice . <~~That's redundant. "The narrator can tell the story in first-person voice." <~~more concise
http://grammar.ccc.commnet.edu/grammar/concise.htm
2) Forget this; see #5 below!
3a) Characters can be divided into flat and round categories. The former are built on a single psychological trait, whereas the latter change their personality during the action.
3b) Characters can be presented in two different ways: directly and indirectly. When the presentation is direct, the character tells the readers about himself directly.
4) Characters can be major or minor. A further distinction can be made between flat and round characters.
5) A first-person narrator can have the following functions: First, he/she conveys an impression of reality,
of restricting the reader’s point of view, and of bringing the reader close to the feelings of the narrator.
6) Join the various types of characters using appropriate links, such as "a first distinction can be made between flat and round characters.
1) The correct pronoun to use in this sentence is "who," as the narrator is a person. The revised sentence would be: "The narrator can be a first-person narrator who uses the first-person voice."
2) The sentence is grammatically correct, but for clarity, it would be better to rephrase it as: "He can be used to bring the reader close to the feelings of the narrator, to convey a sense of reality, and to limit the reader's perspective."
3) The revised sentence would be: "Characters can be divided into flat and round. The former are built on a single psychological trait, while the latter undergo changes in their personality throughout the story."
4) The revised sentence would be: "Characters can be presented in two different ways: directly or indirectly. In direct presentation, the character speaks about themselves."
5) The revised sentence would be: "Characters can be classified as major or minor, and further distinction can be made between flat and round characters."
6) The revised sentence would be: "Connect the various types of characters using appropriate linkers, such as 'A first distinction can be made between flat and round characters.'"