Нужно связаться с банком.

Нужно means it is necessary / it is needed / one must.

In this sentence, Russian uses an impersonal construction:

• Нужно связаться с банком.
• Literally: It is necessary to get in touch with the bank.

There is no explicit subject like I or you. English often says I need to... or You need to..., but Russian very often uses this more general structure.

You can add a person if needed:

• Мне нужно связаться с банком. = I need to contact the bank.
• Вам нужно связаться с банком. = You need to contact the bank.

Связаться is the correct verb here because it means to get in touch / to contact.

A very important point is that Russian verbs come in aspectual pairs.

Here:

• связываться = imperfective
• связаться = perfective

In this sentence, the perfective verb is used because it refers to achieving a result: making contact successfully.

So:

• Нужно связаться с банком. = It is necessary to contact the bank / get in touch with the bank.

By contrast:

• связываться often suggests the process, repetition, or general activity
• связаться suggests one completed act of making contact

Связать without -ся usually means to tie or to connect/link something, so it is a different verb in meaning.

The -ся ending is part of the verb and changes its meaning.

Compare:

• связать = to tie, bind, connect
• связаться = to get in touch, make contact

So here -ся does not simply mean oneself in a literal way. It is just part of the standard verb связаться с кем-то / с чем-то, meaning to contact / get in touch with someone or something.

This is a very common pattern in Russian: a verb with -ся can develop a meaning that is not fully predictable from the non--ся form.

Because the verb связаться requires the preposition с.

The pattern is:

• связаться с кем? с чем?
• to get in touch with whom? with what?

After с in this meaning, Russian uses the instrumental case.

So:

• банк = nominative dictionary form
• с банком = instrumental, meaning with the bank

Other examples:

• связаться с клиентом = to contact the client
• связаться с менеджером = to contact the manager
• связаться с компанией = to contact the company

Because банк is a masculine noun, and in the singular instrumental case it usually takes -ом.

So:

• банк → банком

This matches the preposition с in this expression:

• с банком = with the bank

A few more masculine examples:

• договор → с договором
• клиент → с клиентом
• отдел → с отделом

So if you see с + noun meaning with, instrumental is often what you need.

Yes, Надо связаться с банком is also correct.

Both надо and нужно can mean need to / must / it is necessary.

Very roughly:

• надо is often a bit more conversational
• нужно can sound slightly more neutral or formal

In many everyday contexts, they are interchangeable:

• Мне надо позвонить.
• Мне нужно позвонить.

Both mean I need to call.

So in your sentence, both versions work well.

Because Russian infinitives do not use a separate word like English to.

The infinitive is just the verb form itself:

• связаться = to get in touch / to contact
• позвонить = to call
• сделать = to do / to make

So:

• Нужно связаться с банком. Literally: Necessary contact-INF with bank.

English needs to before most infinitives, but Russian does not.

Yes, Russian word order is fairly flexible, although each version can sound slightly different in emphasis.

The neutral order is:

• Нужно связаться с банком.

You might also hear:

• С банком нужно связаться.

This can put more focus on with the bank.

In most learner situations, it is best to use the neutral order unless you have a reason to emphasize something.

It can absolutely mean I need to contact the bank, depending on context.

Because Russian often omits the person when it is understood, Нужно связаться с банком may mean:

• It is necessary to contact the bank
• We need to contact the bank
• You need to contact the bank
• I need to contact the bank

If you want to make the person explicit, add it:

• Мне нужно связаться с банком. = I need to contact the bank
• Тебе нужно связаться с банком. = You need to contact the bank
• Нам нужно связаться с банком. = We need to contact the bank

Not exactly.

• связаться с банком = to get in touch with the bank / contact the bank
• позвонить в банк = to call the bank

So позвонить в банк is more specific: the method is a phone call.

But связаться с банком is broader. You could do it by phone, email, chat, etc.

That is why связаться с банком is often a little more general than позвонить в банк.