Les meves filles van demanar postres i aigua.

In standard Catalan, possessives usually come with a definite article. So les meves filles is the normal neutral way to say my daughters.

Here:

• les = feminine plural the
• meves = feminine plural my
• filles = daughters

So Catalan literally has the structure the my daughters, even though English does not.

Because the possessive has to agree with the noun it describes.

Filles is:

• feminine
• plural

So the possessive must also be feminine plural:

• meu = my, masculine singular
• meva = my, feminine singular
• meus = my, masculine plural
• meves = my, feminine plural

That is why meves is the correct form here.

Van demanar is a past tense, specifically the very common Catalan periphrastic past.

It is formed with:

• a present-tense form of anar = to go
• plus an infinitive

So:

• van = third person plural form
• demanar = to ask for / request / order

Together, van demanar means asked for or ordered.

No, not in this sentence.

Even though van comes from anar = to go, in van demanar it is functioning as part of the past tense, not as a verb of movement.

So here it means:

• they asked for
• they ordered

If you really wanted to say they went to ask, you would normally say van anar a demanar.

Catalan does have one-word past forms, such as demanaren, but the van + infinitive pattern is extremely common and very natural in modern Catalan.

So:

• van demanar = very common everyday past
• demanaren = also possible, but often more literary, formal, or regional depending on the variety

For most learners, van demanar is the form you will see and hear very often.

Because Catalan often leaves out the article with things being requested, ordered, eaten, or drunk when they are not specific, already-identified items.

So:

• van demanar postres = they ordered dessert
• van demanar aigua = they asked for water

This feels similar to English using bare nouns in phrases like order dessert or drink water.

If you add the article, it can sound more specific or more tied to the context:

• les postres = the dessert(s)
• l’aigua = the water

But the version without the article is very natural here.

Usually, yes.

In standard Catalan, postres is normally used as a plural noun meaning dessert or the dessert course, even when English uses singular dessert.

So Catalan often says:

• menjar postres = to have dessert
• demanar postres = to order dessert

This is one of those places where Catalan and English organize the idea differently.

Yes, aigua is feminine.

If it had an article, you would say:

• l’aigua

Because it begins with a vowel, la becomes l’ before it. But the noun is still feminine.

You can see that with adjectives:

• aigua freda = cold water

The adjective freda is feminine, which confirms the gender.

I simply means and.

So:

• postres i aigua = dessert and water

A useful point for English speakers who also know Spanish: in Catalan, i stays i before words beginning with i or another vowel. It does not normally change the way Spanish y can change to e.

So i aigua is completely normal.

A rough guide:

• filles ≈ FEE-lyəs in more traditional pronunciation, though in some accents it sounds closer to FEE-yəs
• aigua ≈ EYE-gwa or EYE-gwə, depending on the accent

A couple of details:

• The ll in filles is a special Catalan sound. In some varieties it is a true ly sound; in others it is closer to y.
• In Central Catalan, the final unstressed a in aigua is often a weak uh/schwa sound.

Demanar has a broad meaning: to ask for, to request, and in many contexts to order.

So in a restaurant sentence like this, van demanar postres i aigua would very naturally mean:

• they ordered dessert and water

In another context, demanar might simply mean ask for:

• demanar ajuda = ask for help
• demanar un favor = ask for a favor

So the exact English translation depends on the situation.