I really have problems in correcting the grammar and choosing the proper synonyms in these sentences. I selected the six most difficult ones.

1) Their task was to grow and harvest sugar cane. In those profit-making enterprises a system of terrible punishments and rewards was developed (better: devised, adopted are possible?) in order to increase the productivity and to avoid rebellions.
2)The abolitionists gathered in (into, ?) the Republican Party.
3)Orwell speaks about this future state (tells about?), which is constantly in war in order to satirize present society.
4)Citizens don’t know anything about who actually are the members of the Party and what is their purpose. (anything about the Party members and their objectives.)
5)The question of slavery was most urgent (when can I use the superlative without the article?).
6) Through the window pane of his apartment he can see some posters. One of these represents(better:portrays, depicts?) Big Brother, a black-moustached man.

2) in

4) you might reword to: who the members ac tually are of the Party and what their purpose is.

5) this is a good example, with "most" or "very" etc.

The things in parantheses are all possible; some are better than others.

Sra

I agree with Sra. I would add only one thing.

In #3, don't use "speaks" or "tells" -- use "writes" since it's his book you're referring to, right? Or did you hear him speak?

1) In this sentence, you can replace "developed" with "devised" as it is a more specific and appropriate word choice in this context. "Adopted" can also work, but it implies that the system was chosen or accepted by someone else, rather than being created. Both options are correct.

Revised sentence: In those profit-making enterprises, a system of terrible punishments and rewards was devised in order to increase productivity and avoid rebellions.

2) In this sentence, you can use either "in" or "into" depending on the intended meaning. "In" suggests that the abolitionists gathered inside the Republican Party, implying they became part of it. "Into" suggests that the abolitionists joined the Republican Party from outside, implying they were not previously members.

Revised sentence: The abolitionists gathered in/into the Republican Party.

3) In this sentence, you can replace "speaks about" with "tells about" to provide a more precise and vivid description of Orwell's intention. Both options are grammatically correct, but "tells about" conveys a clearer sense of storytelling.

Revised sentence: Orwell tells about this future state, which is constantly at war in order to satirize present society.

4) In this sentence, you can rephrase it to make it more concise and clear. Also, it is grammatically correct to include the definite article "the" before "Party members" and "objectives" to specify which members and objectives are being referred to.

Revised sentence: Citizens know nothing about the Party members and their objectives.

5) The superlative form can be used without the article when it is used in a general or abstract sense. However, in this specific sentence, it sounds more natural to include the article "the" before "most urgent" to indicate a specific urgency.

Revised sentence: The question of slavery was the most urgent.

6) In this sentence, you can replace "represents" with "portrays" or "depicts" to convey a more descriptive and vivid image.

Revised sentence: Through the window pane of his apartment, he can see some posters. One of these portrays Big Brother, a black-moustached man.