As promised, I included 5 sentences. I hope the others were possible!

1) Winston lives a squalid existence in a one-room apartment in "Victory Mansions", eats black bread, synthetic meals, and drinks industrial-grade "Victory Gin."
2) He is discontent with his lifestyle, and keeps a diary of his negative thoughts and opinions about the Party. Winston knows that if his journal is found, he will be tortured and executed by the Thought Police.
3) The Ministry of Truth, which exercises complete control over all media in Oceania, employs Winston at the Ministry's Records Department, where he doctors/alters historical records in order to comply with the Party's version of the past.
4) While Winston likes fabricating a never-ending vision of historic facts, he is also fascinated by the real past, and tries to find out more about the forbidden truth.
5)In Part he encounters Julia, a mechanic on the novel-writing machines, at the Ministry of Truth, and the two begin a necessarily clandestine relationship. They regularly meet in the countryside, away from the surveillance, or in a room above an antique shop.

What you should notice by now is that most corrections/suggestions I make are pretty darned minor!! You're writing has improved and improved, and nearly every single sentence is fine as you have written it.

1. I'd remove all the quotation marks. (Or are you quoting someone?)

2. Remove the first comma.

3. OK

4. OK

5. I don't understand "In Part" -- ?? Otherwise, #5 is OK.