Després de la classe, tornaré a casa amb la meva germana.

Because després normally needs the preposition de before a noun.

• després de la classe = after class
• després by itself usually means afterwards / later

So:

• Després de la classe = after the class
• Després, tornaré a casa = Afterwards, I’ll go home

Després means after or afterwards, depending on how it is used.

In this sentence, després de la classe means after class.

A few useful patterns:

• després de + noun = after something
  
  • després de la classe
• després de + infinitive = after doing something
  
  • després de menjar = after eating
• després alone = afterwards / later
  
  • Després anirem al parc = Afterwards we’ll go to the park

Catalan often uses the definite article where English may omit it.

So la classe literally looks like the class, but in context it naturally translates as class or the class depending on the situation.

In everyday Catalan, saying després de la classe is very normal.

Tornaré is the 1st person singular future of tornar.

• tornar = to return / to go back
• tornaré = I will return / I will go back

The ending -é marks the future for jo.

For example:

• tornaré = I will return
• tornaràs = you will return
• tornarà = he/she will return

In this sentence, tornaré a casa means I’ll go back home or I’ll return home.

Yes. Tornar basically means to return, to go back, or sometimes to come back, depending on context.

In tornar a casa, it means to go back home.

This is very natural Catalan. Even if English might often say go home, Catalan commonly uses tornar a casa when the idea is returning home.

Because a casa is a fixed, very common expression meaning home or to home / at home, depending on context.

• anar a casa = to go home
• ser a casa = to be at home
• tornar a casa = to go back home

If you say a la casa, that usually means to the house, referring to a specific building rather than the idea of home.

So:

• tornaré a casa = I’ll go home
• aniré a la casa de la Maria = I’ll go to Maria’s house

This is a very common feature of Catalan.

With family members, Catalan normally uses:

definite article + possessive + noun

So:

• la meva germana = my sister
• el meu germà = my brother
• la seva mare = his/her mother

This is different from English, which usually uses only the possessive: my sister.

So amb la meva germana is exactly what you would expect in standard Catalan.

Normally, no. Standard Catalan uses the article here:

• amb la meva germana = correct

Without the article, it sounds incomplete or nonstandard in most contexts.

The article is especially normal with family relationships and many everyday nouns when used with possessives.

In some varieties, yes.

ma, mon, mos, etc. are shorter possessive forms that exist in Catalan, especially in certain dialects or more traditional/literary styles:

• ma germana = my sister
• mon pare = my father

But for most learners, la meva germana is the safest and most widely useful standard form.

Amb means with.

So:

• amb la meva germana = with my sister

It is the normal everyday word for with in Catalan.

Examples:

• Vaig amb tu = I’m going with you
• Cafè amb llet = coffee with milk

Catalan word order is fairly flexible, but this order is very natural.

It follows this pattern:

• time expression: Després de la classe
• verb: tornaré
• destination: a casa
• companion: amb la meva germana

So it feels like:

After class, I’ll go home with my sister.

You could change the order in some contexts, but this version is straightforward and idiomatic.

It is natural and helpful because Després de la classe is an introductory time phrase.

So the comma separates that opening element from the main clause:

• Després de la classe, tornaré a casa amb la meva germana.

In informal writing, some people may omit it, but using the comma is a good choice.

The accent in tornaré shows that the stress falls on the last syllable:

tor-na-RÉ

That is important, because without the accent the stress pattern would be different.

A rough pronunciation guide:

• Després ≈ des-PRES
• classe ≈ CLA-sə / CLAS-sə
• tornaré ≈ tor-na-RE
• germana ≈ jer-MA-na

The exact pronunciation varies a bit by dialect, but the written accent always tells you where the stress goes.

Yes, and that is a very useful thing to know.

Catalan tornar a + infinitive can mean to do again:

• Torno a llegir el missatge = I read the message again

But in your sentence, tornar is not followed by another verb. It is followed by a casa, so here it means to return / go back:

• tornar a casa = to go back home

So the meaning depends on what comes after tornar.

Yes. That is a perfectly possible translation.

Depending on context:

• classe could be class or lesson
• tornar could be return, go back, or sometimes simply go
• a casa could be home

So several English versions are possible, such as:

• After class, I’ll go home with my sister.
• After the lesson, I’ll return home with my sister.
• After class, I’ll go back home with my sister.

All of those fit the Catalan sentence well.