Бедному человеку нужна помощь.

Because this sentence uses the pattern кому нужна помощь? = who needs help?

In Russian, the person who needs something is often put in the dative case. So:

• бедный человек = poor person
• бедному человеку = to a poor person / for a poor person

Both words change because the adjective must agree with the noun:

• бедный → бедному
• человек → человеку

So the structure is basically:

• бедному человеку = to the poor person
• нужна помощь = help is needed

Literally, Russian is closer to Help is needed for the poor person than to the English structure The poor person needs help.

No. Человек means person / human being, not specifically man.

It is grammatically masculine, so adjectives agreeing with it also take masculine forms. That is why you get бедному человеку, not a feminine form.

So:

• человек = person
• grammatical gender: masculine
• real-world meaning: can refer to any person unless context says otherwise

This is a common Russian pattern: grammatical gender does not always equal biological sex.

Because нужна agrees with помощь.

The noun помощь is:

• feminine
• singular

So the form must also be feminine singular:

• нужен — masculine singular
• нужна — feminine singular
• нужно — neuter singular
• нужны — plural

Compare:

• Мне нужен совет. = I need advice.
• Мне нужна помощь. = I need help.
• Мне нужно время. = I need time.
• Мне нужны деньги. = I need money.

It is in the nominative singular.

In this construction, the thing that is needed is treated as the grammatical subject:

• помощь нужна = help is needed

So:

• бедному человеку = dative, the person who needs something
• помощь = nominative, the thing needed

That is why помощь does not change here.

Not exactly. Here нужна is the short form of the adjective нужный = needed / necessary.

Russian often uses these short forms as the predicate:

• нужен
• нужна
• нужно
• нужны

So Бедному человеку нужна помощь is literally something like:

• Help is necessary/needed for the poor person

In natural English, though, we usually translate it as:

• The poor person needs help

Because in the present tense, Russian normally leaves out to be.

So where English says:

• Help is needed

Russian just says:

• Помощь нужна

There is no present-tense is word in ordinary Russian sentences like this.

Yes. Russian word order is more flexible than English because case endings show the grammatical roles.

These are all possible:

• Бедному человеку нужна помощь.
• Помощь нужна бедному человеку.

The core meaning stays the same, but the focus changes a little:

• Бедному человеку нужна помощь puts attention first on the person.
• Помощь нужна бедному человеку puts attention first on help.

So the original sentence is perfectly natural, but it is not the only possible order.

Because Russian has no articles.

So бедному человеку could mean:

• to a poor person
• to the poor person

and помощь could be:

• help
• the help

Context tells you which is meant.

That is very normal in Russian, and learners have to get used to relying on context instead of articles.

Yes. A very common alternative is:

• Бедный человек нуждается в помощи.

This uses a different structure:

• бедный человек = nominative subject
• нуждается = needs / is in need
• в помощи = in help, after нуждаться в

So you have two useful patterns:

1. Кому нужна помощь?
   Бедному человеку нужна помощь.

2. Кто нуждается в помощи?
   Бедный человек нуждается в помощи.

The first pattern is often simpler and very common in everyday Russian. The second can sound a bit more formal or written.

The stress is:

• Бе́дному челове́ку нужна́ по́мощь.

A rough pronunciation guide:

• Бе́дному → BYED-na-mu
• челове́ку → chi-la-VYE-ku
• нужна́ → noozh-NA
• по́мощь → PO-mashch

A couple of useful notes:

• Unstressed о is often pronounced more like a.
• ч is like ch in check.
• ж is like the s in measure.
• The final щ in помощь is a soft, long sh-like sound.