Help interpreting this sentence

Question

I have trouble understanding the sentence below

文章が長くならないよう、必要のない部分は省略した

I roughly translate: literature doesn't need to be long, omit unnecessary part

• Can I use passive form “unnecessary part was omitted” instead?
• How should I interpret ならないよう、必要のない部分. I don’t understand why のis there

Answer 1

• dictionary-form + よう means "so as to ～", "so that ～", etc. See this article.
• 必要のない部分 literally means "the part where there is not necessity". 必要のない is a relative clause that adjectivally modifies 部分, and の can be used in place of が in relative clauses. See: How does the の work in 「日本人の知らない日本語」? Of course you can simply translate it as "unnecessary parts".
• した is not an imperative form. This sentence is not an order but a neutral sentence with the omitted subject (="I"). The last half literally means "I omitted unnecessarily parts", but you can translate it also as "unnecessary parts were omitted".