Question

Thank you very much. I included my corrections in brackets, when necessary.

1)The front door is where Dr Jekyll is seen and represents his public face.
2)His friend moves like a guttering candle which is about to go out.He describes the face of his dying friend, his skin which is starting to fall off and his eyes which are writhing (or writhing eyes).
3)The poet is horrified by chemical warfare since he has seen his friend’s death. ( the poet has been horrified by chemical warfare ever since he saw his friend dying)
4)There is a similarity with the myth of Faust ( better: between Dorian and Faust) since they both sold (not sell) their souls to the devil to have their desires satisfied. (can you say “in exchange for absolute knowledge and eternal youth respectively). Killing the picture means killing himself. (is the gerund correct?)
5)He realizes his personality is made of two parts. The duality of man’s nature is also represented by the two sides of the doctor’s house: the front entrance is nice whereas the rear one is dark and ugly.
6)In the first part of the novel Lord Henry’s point of view is adopted/used, whereas in the second one Dorian’s. Life must be lived for art (better for art’s sake) forgetting moral responsibility.

Answer 1

1. OK

2. Owen describes the face of his dying friend, whose skin is starting to fall off and whose eyes are writhing. His friend moves like a guttering candle.
<b>Please note ALL corrections. You don't need "which is about to go out" because that's what "guttering" means. You cannot place "friend" and "his skin" directly next to each other because they are NOT appositives. Etc.</b>

3. Either phrasing is fine; just don't mix the two.

4. Yes, use the "between" phrasing; use "sell" not "sold." The first sentence here is terribly awkward. Try this instead:
There is a similarity between Dorian and Faust since they both sell their souls to the devil to have all their desires met.

5. Capital T -- comma needed

6. Comma needed; use "adopted"; use "for art's sake"