Levo je banka, a desno apoteka.

Because levo and desno are functioning as adverbs, meaning on the left and on the right.

By contrast, leva and desna are adjectives, so they have to describe a noun:

• leva strana = left side
• desna ruka = right hand

So in this sentence, Serbian uses the adverbial forms to describe location:

• Levo je banka = The bank is on the left
• Desno apoteka = The pharmacy is on the right

Here they express position, not movement.

So:

• levo = on the left / to the left
• desno = on the right / to the right

The sentence is describing where things are located.

If you wanted movement, Serbian often uses forms like:

• nalevo = to the left
• nadesno = to the right

For example:

• Skreni nalevo. = Turn left.

Both versions are correct.

Serbian often omits repeated words when they are easy to understand from context. So:

• Levo je banka, a desno apoteka.
• Levo je banka, a desno je apoteka.

Both mean the same thing. The version without the second je sounds a bit more compact and natural in quick description.

In this sentence, a is best understood as and, while, or whereas.

It often connects two pieces of information that are being contrasted or set side by side:

• Levo je banka, a desno apoteka. = On the left is a bank, and on the right a pharmacy.

So it is not a strong but here. It is more like:

• and meanwhile
• while
• whereas

Also, the comma before a is normal in Serbian punctuation.

Because Serbian word order is more flexible than English word order.

Both are possible:

• Levo je banka.
• Banka je levo.

The difference is mainly emphasis:

• Levo je banka puts the focus first on location
• Banka je levo puts the focus first on the bank

In directions or scene description, starting with levo/desno is very natural.

Because Serbian has no articles.

English uses:

• a bank
• the bank

Serbian usually just says:

• banka

Whether it means a bank or the bank depends on context.

So:

• banka can mean a bank or the bank
• apoteka can mean a pharmacy or the pharmacy

They are in the nominative singular.

You can tell because these are the basic dictionary forms:

• banka
• apoteka

In a sentence like this, the nouns stay in the nominative because they are the main nouns being identified in the statement.

You can compare:

• Banka je levo.
• Apoteka je desno.

Same forms, still nominative.

Yes. Apoteka is the normal everyday Serbian word for pharmacy or drugstore/pharmacy.

It is a common and standard word, so there is nothing unusual about it in this sentence.

Yes. A more explicit version would be:

• S leve strane je banka, a s desne strane apoteka.
• Na levoj strani je banka, a na desnoj apoteka.

These mean essentially the same thing, but they sound a bit more spelled out:

• on the left side
• on the right side

The original sentence is shorter and very natural in everyday speech.

It is natural Serbian.

It sounds like something someone would say when:

• giving directions
• describing what they see
• explaining the layout of a street or room

A speaker might also say:

• Levo je banka, a desno je apoteka.
• Banka je levo, a apoteka desno.

All of these are natural, with small differences in rhythm and emphasis.

Not in this sentence.

For simple location, Serbian normally uses:

• levo
• desno

or fuller expressions like:

• na levoj strani
• na desnoj strani

Na levo and na desno are not the normal forms here.

For movement, Serbian often uses:

• nalevo
• nadesno

So a useful contrast is:

• Levo je banka. = The bank is on the left.
• Idi nalevo. = Go left.