Перед сном я не хочу листать новости в телефоне.

Because перед requires the instrumental case.

The dictionary form is сон = sleep.
In the instrumental singular, it becomes сном.

So:

• перед сном = before sleep / before bed

This is a very common pattern:

• перед работой — before work
• перед ужином — before dinner
• перед встречей — before the meeting

So the important rule is:

• перед + instrumental

In real usage, it usually means before going to sleep / before bed.

It does not have to mean the exact moment right before you fall asleep. It can refer to that general bedtime period, for example when you are already lying in bed or winding down for the night.

So in English, before bed is often the most natural translation.

Yes, Russian can often omit the subject pronoun when it is clear from the verb.

So both are possible:

• Перед сном я не хочу листать новости в телефоне.
• Перед сном не хочу листать новости в телефоне.

The version with я is a little more explicit and neutral.
The version without я sounds more conversational, diary-like, or context-dependent.

So я is not required for grammar, but it is completely natural here.

This is the normal Russian pattern for want to do something:

• хотеть + infinitive

So:

• хочу листать = I want to scroll/browse
• не хочу листать = I do not want to scroll/browse

The negation не goes with хочу, because that is the finite verb:

• я не хочу = I do not want

Then листать stays in the infinitive.

So the structure is:

• Перед сном — time phrase
• я — subject
• не хочу — main verb
• листать — infinitive
• новости в телефоне — what is being scrolled through / where

Листать originally means to flip through pages, but it is also used for modern screen behavior like scrolling through content.

So:

• читать новости = to read the news
• листать новости = to browse / scroll through the news

The second one suggests a more casual, less focused action. You are moving through headlines or posts, not necessarily reading every article carefully.

That is why листать fits very well with phones and news feeds.

In Russian, новости is grammatically a plural noun.

So although English says:

• the news is...

Russian says:

• новости = news, but grammatically plural

Examples:

• Эти новости плохие. — This news is bad.
• Я читаю новости. — I read the news.

In your sentence, новости is in the accusative plural, but because it is inanimate, the accusative form looks the same as the nominative:

• nominative: новости
• accusative: новости

So the form does not change.

This is one of those places where Russian and English use different prepositions.

In Russian, в телефоне can naturally mean in/on the phone, especially when talking about content inside the device, apps, feeds, messages, and so on.

So:

• листать новости в телефоне = scroll through the news on your phone
• сидеть в телефоне = spend time on your phone
• искать что-то в телефоне = look for something on your phone

English prefers on my phone, but Russian often uses в here.

Also, do not confuse this with:

• по телефону = by phone / on the phone in the sense of a phone call

So по телефону would not work in this sentence.

Sometimes yes, but the nuance can shift.

Very roughly:

• в телефоне often focuses on something inside the phone, like content, apps, messages, feeds
• на телефоне can sometimes be used for something on the device or on the screen

In everyday speech, в телефоне is very common for this kind of idea, especially when talking about spending time scrolling or looking through content.

So in this sentence, в телефоне sounds natural and idiomatic.

Russian often leaves out possessives like my, your, his when the owner is obvious from context.

Here, because the speaker says я and is talking about a personal bedtime habit, listeners will usually assume it means my phone unless there is reason to think otherwise.

So:

• в телефоне = in/on the phone
• в моём телефоне = in/on my phone
• в своём телефоне = in/on one’s own phone

Adding моём or своём is possible, but it is not necessary unless you want emphasis or contrast.

For example:

• Я не хочу листать новости в своём телефоне, лучше почитаю книгу.

Here своём adds a bit of contrast: my own phone, not something else.

Листать is imperfective, and that fits the sentence well because the speaker is talking about the activity in general, not about completing it once.

With хотеть, Russian often uses the imperfective when referring to an action as a process or habit:

• хочу читать
• хочу смотреть
• не хочу листать

Here the meaning is something like:

• I do not want to engage in that activity before bed.

A perfective form would sound more like a single completed action with a result. For example, a verb like пролистать could suggest scroll through once / go through all of it.

So:

• не хочу листать = I do not want to be scrolling/browsing
• не хочу пролистать would sound much less natural for this general idea

Yes. Russian word order is flexible, and changing it usually changes emphasis, not the core meaning.

Your sentence:

• Перед сном я не хочу листать новости в телефоне.

This puts перед сном first, so the time frame is highlighted.

Other possible orders:

• Я не хочу перед сном листать новости в телефоне.
  More straightforward, closer to English order.

• Новости в телефоне я перед сном листать не хочу.
  More contrastive or emphatic, as if stressing news on the phone in particular.

So the original version is very natural, especially if the speaker wants to foreground the idea of before bed.