Na rogu ulicy jest bankomat.

Because na can take different cases depending on the meaning.

Here it expresses location: on/at the corner, so na takes the locative case.

• róg = corner
• na rogu = on/at the corner

If there were movement toward the corner, you would use the accusative instead:

• Idę na róg ulicy. = I’m going to the street corner.

So in Na rogu ulicy jest bankomat, we are describing where something is, not where something is going.

Because ulicy is the genitive singular of ulica.

In Polish, when one noun is connected to another in a phrase like the corner of the street, the second noun is often put in the genitive:

• róg ulicy = the corner of the street
• literally: corner street-GEN

So:

• ulica = street
• ulicy = of the street

This is very common in Polish:

• drzwi domu = the door of the house
• środek miasta = the center of the city

In natural English, it usually corresponds to on the corner or at the corner, depending on context.

Polish na often does not match English on literally. In this sentence, na rogu ulicy means the ATM is located at/on the street corner.

So although na often means on, here you should learn the whole expression:

• na rogu = on/at the corner

Jest is the 3rd person singular form of być = to be.

In this sentence, jest works like there is in English:

• Na rogu ulicy jest bankomat.
• literally: At the corner of the street is an ATM.
• natural meaning: There is an ATM on the street corner.

Polish often uses jest to say that something exists or is located somewhere.

Usually not in this kind of neutral sentence.

• Na rogu ulicy bankomat sounds incomplete or unnatural in standard Polish.
• Na rogu ulicy jest bankomat is the normal full sentence.

Polish sometimes drops forms of to be in very informal speech or in special styles, but for learners, you should treat jest as necessary here.

Polish word order is more flexible than English, but the sentence as given is very natural because it first gives the location and then introduces what is there.

• Na rogu ulicy jest bankomat. = very natural
• literally: At the street corner there is an ATM.

This structure is common when introducing new information.

Other word orders are possible, but they can sound more marked or emphasize something different:

• Bankomat jest na rogu ulicy. = The ATM is on the street corner.
  This sounds more like you are talking about the ATM specifically.

Yes. Bankomat is a masculine inanimate noun.

That matters for agreement and case endings.

For example:

• ten bankomat = this ATM
• widzę bankomat = I see an ATM
• nie ma bankomatu = there is no ATM / there isn’t an ATM

Since it is masculine singular, the verb here is also singular:

• jest bankomat

The dictionary forms are:

• na = on, at
• róg = corner
• ulica = street
• być = to be
• bankomat = ATM / cash machine

In the sentence, some words change form:

• róg → rogu because of the locative after na
• ulica → ulicy because of the genitive after róg
• być → jest because it is he/she/it is

Normally, no.

For street corners, Polish usually says:

• na rogu ulicy = on/at the street corner

Using w rogu usually means in the corner of something enclosed, like a room:

• w rogu pokoju = in the corner of the room

So:

• na rogu ulicy = at the corner of the street
• w rogu pokoju = in the corner of the room

This is an important expression to memorize as a whole.

A simple approximate pronunciation for an English speaker is:

nah ROH-goo oo-LEE-tsih yest ban-KOH-mat

A few helpful details:

• r is rolled or tapped
• g in rogu is always a hard g
• c in ulicy sounds like ts
• j in jest sounds like English y
• stress is usually on the second-to-last syllable:
  • RO-gu
  • u-LI-cy
  • BAN-ko-mat

You would say:

Na rogu ulicy są bankomaty.

Changes:

• jest → są = are
• bankomat → bankomaty = ATMs

So:

• Na rogu ulicy jest bankomat. = There is an ATM on the street corner.
• Na rogu ulicy są bankomaty. = There are ATMs on the street corner.

Yes. A slightly more formal or written alternative is:

Na rogu ulicy znajduje się bankomat.

This also means There is an ATM on the street corner or An ATM is located on the street corner.

Compare:

• Na rogu ulicy jest bankomat. = neutral, simple, everyday
• Na rogu ulicy znajduje się bankomat. = a bit more formal

For everyday speech, the original sentence is completely normal and natural.