Хоть бы завтра в магазине снова были креветки и тунец.

In this sentence, хоть бы expresses a wish or hope, often with a slightly emotional tone.

So Хоть бы завтра в магазине снова были креветки и тунец means something like:

• If only there were shrimp and tuna in the store again tomorrow
• I hope they have shrimp and tuna in the store again tomorrow

A few important points:

• хоть бы is not literal at least here.
• It often conveys strong hope, longing, or mild frustration.
• It is very common in conversational Russian.

So the speaker is not just stating a fact. They are wishing for it.

This is one of the most confusing things for English speakers, but it is normal in Russian.

After бы in wish or unreal/desired situations, Russian often uses the past tense form of the verb:

• Хоть бы были...
• Если бы были...
• Хорошо бы было...

Even though the meaning can refer to the present, future, or an unreal situation.

So here:

• завтра tells you the time is future
• были is used because the construction with бы requires the past-form verb

In other words, были here does not mean literal past time. It is part of a grammar pattern used for wishes and hypothetical situations.

Because the subject is effectively креветки и тунец together.

That is a compound subject:

• креветки = shrimp
• тунец = tuna

Together they mean shrimp and tuna, so the verb agrees in the plural:

• были креветки и тунец

Compare:

• Были креветки. = There was/were shrimp.
• Был тунец. = There was tuna.
• Были креветки и тунец. = There were shrimp and tuna.

Even though тунец is singular by itself, the whole combination is plural.

Because after в meaning in, when you are talking about location, Russian uses the prepositional case.

The base form is:

• магазин = store/shop

After в for location:

• в магазине = in the store

So:

• завтра в магазине = tomorrow in the store

This is a standard pattern:

• в доме = in the house
• в школе = at school / in the school
• в ресторане = in the restaurant

If в meant motion into somewhere, you would usually use the accusative instead:

• в магазин = to the store / into the store

But here it is location, so в магазине is correct.

Russian often does not use a separate word like English there is / there are.

Instead, it can simply say:

• В магазине были креветки и тунец. = There were shrimp and tuna in the store.

Literally, this is closer to:

• In the store were shrimp and tuna

Russian commonly expresses existence this way: location + verb + thing.

In your sentence, the idea is:

• Хоть бы ... были креветки и тунец = If only there were shrimp and tuna

So nothing is missing. This is a normal Russian way to express there is/are.

This reflects how the foods are being viewed.

• креветки is commonly used in the plural when talking about shrimp as food items
• тунец is commonly used in the singular when talking about tuna as a food product

So Russian naturally says:

• креветки = shrimp
• тунец = tuna

This is similar to how English sometimes treats food nouns differently:

• shrimp can feel like multiple pieces
• tuna often feels like a mass food noun

Russian could use other forms in other contexts, but in a grocery/food context, креветки и тунец sounds very natural.

снова means again.

So it tells us that shrimp and tuna were available before, and the speaker wants that situation to repeat.

Without снова:

• Хоть бы завтра в магазине были креветки и тунец. = If only there were shrimp and tuna in the store tomorrow.

With снова:

• Хоть бы завтра в магазине снова были креветки и тунец. = If only there were shrimp and tuna in the store again tomorrow.

It adds the idea of once more / again.

No, Russian word order is fairly flexible, and this sentence can be rearranged for emphasis.

Your version:

• Хоть бы завтра в магазине снова были креветки и тунец.

This sounds natural. It emphasizes the whole wish with a smooth flow.

Other possible orders include:

• Хоть бы в магазине завтра снова были креветки и тунец.
• Хоть бы завтра снова были в магазине креветки и тунец.
• Хоть бы креветки и тунец завтра снова были в магазине.

These are all understandable, but they may sound slightly different in emphasis or naturalness.

A useful rule:

• Russian word order often changes focus, not basic meaning.

Your sentence is a very normal neutral-emotional order for spoken Russian.

Usually, no.

Even though хоть often relates to ideas like at least or even if, the set expression хоть бы in sentences like this means something more like:

• if only
• I just hope
• let there at least be... only in a very loose emotional sense

So a direct translation with at least would often sound wrong or incomplete in English.

In this sentence, the best interpretation is a wish, not a minimum requirement.

It is mostly conversational and very natural in everyday speech.

Хоть бы is common in spoken Russian when people express:

• hope
• worry
• irritation
• longing

For example:

• Хоть бы не было дождя. = I hope it doesn’t rain.
• Хоть бы он позвонил. = If only he would call.
• Хоть бы успеть. = I hope I make it in time.

So your sentence sounds like something a real person would casually say, not like stiff textbook language.

Not in this structure.

If you say:

• Завтра в магазине снова будут креветки и тунец.

that means:

• Tomorrow there will be shrimp and tuna in the store again.

That is a statement/prediction.

But your original sentence is a wish:

• Хоть бы завтра в магазине снова были креветки и тунец.

Because of хоть бы, Russian uses the past-form verb были.

So:

• будут = future fact/prediction
• были with бы = wish/hypothetical situation

That difference is essential.

It is a complete sentence.

Russian often allows wish-sentences like this without adding anything else:

• Хоть бы всё получилось.
• Хоть бы он пришёл.
• Хоть бы завтра было тепло.

So Хоть бы завтра в магазине снова были креветки и тунец is fully complete and natural.

The speaker’s attitude is understood from хоть бы, and the rest of the sentence gives the desired situation.

Not with exactly the same meaning.

• Хоть бы... expresses a direct wish/hope
• Если бы... literally means if only / if, but it usually sounds like the start of a larger thought, or it can sound more reflective

Compare:

• Хоть бы завтра в магазине снова были креветки и тунец. = I really hope there are shrimp and tuna in the store again tomorrow.

• Если бы завтра в магазине снова были креветки и тунец... = If only there were shrimp and tuna in the store again tomorrow...

  The second one often feels less self-contained unless something follows, though in speech it can also stand alone.

So хоть бы is especially natural for a spontaneous emotional wish.