La meva filla es renta la cara i les mans abans de menjar.

In standard Catalan, possessives usually appear with a definite article:

• el meu llibre = my book
• la meva filla = my daughter

So the normal pattern is:

article + possessive + noun

That is why you get la meva filla, not just meva filla.

Because the possessive adjective agrees with the noun it describes.

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

Since filla is feminine singular, the correct form is meva.

Es renta is the 3rd person singular present form of rentar-se, which means to wash oneself.

Breakdown:

• es = reflexive pronoun (herself / himself / itself depending on the subject)
• renta = washes

So la meva filla es renta means my daughter washes herself.

In this sentence, Catalan then specifies what she washes: la cara i les mans.

Catalan uses a reflexive pronoun when the subject does the action to themself.

Compare:

• Renta el cotxe. = He/She washes the car.
• Es renta. = He/She washes themself.

In La meva filla es renta la cara i les mans, the daughter is washing her own face and hands, so the reflexive es is needed.

With body parts, Catalan usually uses the definite article, especially with reflexive verbs, where the owner is already clear.

So Catalan prefers:

• es renta la cara = washes her face
• es renta les mans = washes her hands

Rather than:

• es renta la seva cara
• es renta les seves mans

Those forms are possible in special contexts, but they sound less natural here. The normal Catalan pattern is reflexive pronoun + definite article + body part.

Because es belongs to the verb renta, not separately to each noun.

The structure is:

• es renta = washes herself
• la cara i les mans = the face and the hands

Both la cara and les mans are objects of the same verb, joined by i (and), so you only need one reflexive pronoun.

Because Catalan uses abans de + infinitive to mean before doing something.

So:

• abans de menjar = before eating
• abans de sortir = before leaving
• abans de dormir = before sleeping

Here menjar is the infinitive to eat.

Here it is a verb: the infinitive to eat.

In abans de menjar, it means before eating.

Catalan infinitives often work where English uses -ing forms:

• abans de menjar = before eating
• després de treballar = after working

So although menjar can also be a noun in other contexts, in this sentence it is verbal.

Because the subject is already expressed as La meva filla.

Catalan does not need an extra subject pronoun if the subject is already stated. In fact, Catalan often drops subject pronouns unless they are needed for emphasis or contrast.

So:

• La meva filla es renta la cara... = My daughter washes her face...
• Ella es renta la cara... would add she, but that would usually sound emphatic: She washes her face...

Yes, to some extent.

The sentence as given has a neutral, natural order:

La meva filla es renta la cara i les mans abans de menjar.

But you could also say:

Abans de menjar, la meva filla es renta la cara i les mans.

That puts more focus on the time expression before eating. Both are correct; the original version is just the more straightforward word order.