In de diepvries ligt nog vis voor morgen, en Sofie koopt ook ham en een courgette voor de picknick.

Dutch often puts a time or place phrase first to set the scene. When that happens in a main clause, the finite verb must still stay in the second position.

So:

• In de diepvries = first element
• ligt = verb in second position
• nog vis = the subject/content after the verb

That is why you get:

In de diepvries ligt nog vis voor morgen.

If you started with the subject instead, you could also say:

Er ligt nog vis in de diepvries voor morgen.

Both are natural, but the original puts more emphasis on where the fish is.

This is because of the Dutch verb-second rule in main clauses.

After the opening phrase In de diepvries, the verb has to come immediately after it:

• In de diepvries ligt ...

So the subject or noun phrase comes later:

• In de diepvries ligt nog vis ...

English does not do this in the same way, which is why it may feel unusual.

Nog is a very common Dutch word with several meanings. In this sentence, it means something like:

• still
• yet
• there is still some

So:

In de diepvries ligt nog vis voor morgen
means there is still fish in the freezer for tomorrow.

It suggests the fish is already there and available.

Because vis here is being used as an uncountable food noun, like fish in English when you mean fish as food in general.

So:

• vis = some fish
• ham = some ham

But courgette is a countable item, so Dutch uses een:

• een courgette = a courgette / a zucchini

Compare:

• Ik koop vis. = I’m buying fish.
• Ik koop een vis. = I’m buying a fish.
  This usually sounds more like one whole fish, not just fish as food in general.

Dutch often uses different verbs for location, depending on how something is positioned.

Common ones are:

• staan = stand
• zitten = sit
• liggen = lie

For many objects, foods, and things that are stored somewhere, Dutch often uses liggen. So:

• De vis ligt in de diepvries.

This is very natural in Dutch, even if English would usually just say is in the freezer.

Both can refer to a freezer.

• de vriezer is the more direct everyday word for the appliance
• de diepvries can also mean the freezer, especially the deep-freeze compartment or frozen-storage idea

In many contexts they overlap. In this sentence, in de diepvries simply means in the freezer.

It is the same preposition, voor, but the meaning is slightly different in each phrase.

• voor morgen = for tomorrow
  This shows time/reference: the fish is meant for tomorrow.

• voor de picknick = for the picnic
  This shows purpose/intended use: the ham and courgette are meant for the picnic.

So voor often means for, but the exact nuance depends on context.

In the second clause, Dutch has normal main-clause word order:

• Sofie = first element
• koopt = second-position verb
• ook = placed after the verb here

So:

Sofie koopt ook ham en een courgette ...

This means Sofie is also buying those things.

You could move ook in other sentences, but its position can change what it emphasizes. In this sentence, the placement is very natural and neutral.

Ook means also / too.

It tells us that Sofie is buying these things in addition to something else already mentioned or understood. In this sentence, it links nicely with the first clause:

• there is still fish for tomorrow,
• and Sofie is also buying ham and a courgette for the picnic.

So ook marks an additional action or additional items.

Because ham is usually treated here as an uncountable food word, just like in English:

• I’m buying ham
  not usually
• I’m buying a ham

So Dutch says:

• ham = some ham
• een courgette = one courgette

If you said een ham, that would usually mean a whole ham as one countable object, which is a more specific idea.

Dutch often uses an article where English might or might not. Here, de picknick refers to a specific picnic that both speaker and listener can identify from the context.

So:

• voor de picknick = for the picnic

If the situation already makes clear which picnic is meant, using de is natural.

Yes, courgette is a normal Dutch word. It means zucchini.

Learners from English-speaking countries may notice a difference:

• British English often uses courgette
• American English usually uses zucchini
• Dutch uses courgette

So the Dutch word may look familiar to British learners.

Yes. A very common alternative is:

Er ligt nog vis in de diepvries voor morgen.

Using er is especially common when introducing the existence of something, similar to English there is.

Compare:

• In de diepvries ligt nog vis voor morgen.
  Emphasis on the location.
• Er ligt nog vis in de diepvries voor morgen.
  More like There is still fish in the freezer for tomorrow.

Both are correct and natural.