Нужно проверить систему.

Нужно is an impersonal word meaning it is necessary / it is needed / one must. Russian often expresses obligation this way without naming a subject.

So Нужно проверить систему literally feels like:

It is necessary to check the system.

This is very natural in Russian, especially when:

• the speaker does not want to say exactly who must do it
• the obligation is general
• the focus is on the task itself

Compare:

• Я должен проверить систему = I must check the system
• Нам нужно проверить систему = We need to check the system
• Нужно проверить систему = The system needs to be checked / We need to check the system / Someone needs to check the system

So нужно does not by itself tell you who has to do it.

Russian often allows subjectless or impersonal sentences. This is one of them.

In English, we usually need a subject:

• We need to check the system
• It is necessary to check the system

In Russian, the subject can simply be omitted if it is unknown, unimportant, or understood from context:

• Нужно проверить систему.

This makes the sentence sound general and practical. It is very common in instructions, technical speech, workplace situations, and everyday conversation.

Проверить is the perfective form, while проверять is imperfective.

Here, проверить is used because the sentence refers to a complete action: checking the system as a finished task.

• Нужно проверить систему. = The system needs to be checked / We need to check the system
  Focus: do the check and complete it.

If you used проверять, it would sound more like:

• a repeated action
• a process in general
• an ongoing activity

For example:

• Нужно проверять систему каждый день. = The system needs to be checked every day.

So in your sentence, проверить is chosen because it means check it once and get it done.

Систему is in the accusative case because it is the direct object of the verb проверить.

The dictionary form is:

• система = system

Its accusative singular form is:

• систему

This happens because проверить что? = check what?

• систему

Since система is a feminine noun ending in -а, the accusative singular changes -а to -у:

• система → систему

Yes. Надо проверить систему is also correct and very natural.

Both надо and нужно can mean need to / must / it is necessary. In many contexts they are very close.

Very roughly:

• надо often sounds a bit more conversational
• нужно can sound a bit more neutral, matter-of-fact, or slightly more formal

But in everyday speech, both are common, and in this sentence the difference is small.

So both work:

• Нужно проверить систему.
• Надо проверить систему.

In this sentence, нужно is being used impersonally, so it stays in this fixed form.

But related forms do exist:

• нужен
• нужна
• нужно
• нужны

Those are used when нужен means is needed and agrees with a noun:

• Нужен специалист. = A specialist is needed.
• Нужна помощь. = Help is needed.
• Нужно время. = Time is needed.
• Нужны документы. = Documents are needed.

However, in Нужно проверить систему, нужно is not agreeing with систему. It is part of the impersonal structure нужно + infinitive.

Both sentences mean essentially the same thing. The difference is mainly word order and emphasis.

• Нужно проверить систему.
  Neutral order. The whole action is presented naturally.

• Систему нужно проверить.
  This puts extra focus on the system. It can sound like:

  • The system needs to be checked
  • It’s the system that needs checking

Russian word order is more flexible than English word order, and moving words around often changes emphasis rather than core meaning.

Yes. Very often Russian uses an impersonal active-looking structure where English might prefer a passive translation.

So:

• Нужно проверить систему

can be translated as:

• We need to check the system
• Someone needs to check the system
• The system needs to be checked

Which translation is best depends on context. Russian does not force you to specify the agent here.

The stress is on the е in вер:

• провЕрить

And систему is stressed on the и:

• систЕму? No — actually систЕма is wrong here.
• Correct stress:
  • систЕма? Let's be careful: the standard stress is систЕма.
  • Therefore accusative singular is систЕму.

So the full sentence is pronounced approximately:

НУжно провЕрить систЕму.

A few pronunciation notes:

• о in unstressed syllables is reduced, so it may sound closer to a or a neutral vowel
• ть at the end of проверить is soft
• ж in нужно is a hard zh sound

No. That is not correct.

If you want to include we, you need:

• Нам нужно проверить систему.

Why? Because with нужно, the person who needs to do something is usually expressed in the dative case:

• мне нужно = I need to
• тебе нужно = you need to
• нам нужно = we need to
• ему нужно = he needs to

So:

• Нужно проверить систему. = It is necessary to check the system
• Нам нужно проверить систему. = We need to check the system

But not:

• Мы нужно проверить систему

Usually context tells you.

Russian speakers often leave the doer unstated when it is obvious from the situation. For example:

• at work, it may mean we need to check it
• in instructions, it may mean someone / the technician / the user needs to check it
• in a report, it may mean the system should be checked

If Russian wants to specify the person, it can do so:

• Мне нужно проверить систему. = I need to check the system
• Тебе нужно проверить систему. = You need to check the system
• Инженеру нужно проверить систему. = The engineer needs to check the system

Without that, the sentence stays general.