No sábado, vou apresentar minha namorada aos meus amigos.

Portuguese often leaves out subject pronouns when the verb already makes the subject clear.
Here, vou is the 1st person singular form, so it already tells you the subject is I.

So both are possible:

• Vou apresentar minha namorada aos meus amigos.
• Eu vou apresentar minha namorada aos meus amigos.

Adding eu usually gives a little extra emphasis or contrast.

No is a contraction of em + o.

• em = in/on
• o sábado = Saturday

So:

• no sábado = on Saturday

Also, sábado is masculine, so it takes o, not a. That is why it is no sábado, not na sábado.

In this sentence, no sábado usually refers to a specific Saturday, depending on context.

In Brazilian Portuguese, ir + infinitive is extremely common for talking about the future, especially in everyday speech.

So:

• vou apresentar = very natural, common spoken Brazilian Portuguese
• apresentarei = also correct, but more formal, more written, or sometimes more dramatic/emphatic

Both mean future time, but vou apresentar is what you will hear very often in conversation.

Here, apresentar means to introduce.

The structure is:

• apresentar alguém a alguém
  = to introduce someone to someone

So in this sentence:

• minha namorada = the person being introduced
• aos meus amigos = the people she is being introduced to

That is why the sentence is built this way.

Because aos is a contraction of a + os.

• a = to
• os meus amigos = my friends

So:

• a + os = aos

This happens very often in Portuguese:

• a + o = ao
• a + a = à
• a + os = aos
• a + as = às

So aos meus amigos literally comes from a os meus amigos.

With possessives in Brazilian Portuguese, the definite article is often optional, especially in many everyday contexts.

So both of these can be natural:

• minha namorada
• a minha namorada

Likewise, both can occur:

• a meus amigos
• aos meus amigos

In your sentence, the speaker uses no article before minha namorada, but does use the article before meus amigos, which creates the contraction aos.

This kind of variation is very normal in Portuguese.

Because possessives in Portuguese agree with the noun that follows, not with the speaker.

• namorada is feminine singular → minha
• amigos is masculine plural → meus

Compare:

• meu namorado = my boyfriend
• minha namorada = my girlfriend
• meu amigo = my male friend
• minha amiga = my female friend
• meus amigos = my friends (all male or mixed group)
• minhas amigas = my female friends

Not necessarily. In Portuguese, the masculine plural is used for:

• a group of all men, or
• a mixed group of men and women

So meus amigos can mean:

• my male friends
• my friends in general, if the group is mixed

If the group were all female, it would be minhas amigas.

Yes. Portuguese allows some flexibility in word order.

For example, this also sounds natural:

• Vou apresentar minha namorada aos meus amigos no sábado.

The version with No sábado at the beginning puts the time first, so it highlights when this will happen.

Both are correct; the difference is mostly about emphasis and flow.

For the meaning introduce someone to someone, the standard pattern is apresentar alguém a alguém.

So the most natural choice is:

• apresentar minha namorada aos meus amigos

Using para is less standard for this meaning and may sound more like present/show in some contexts rather than introduce.

So if you mean introduce, stick with a:

• apresentar alguém a alguém

Yes, in normal everyday Brazilian Portuguese, namorada means girlfriend.

Related forms:

• namorado = boyfriend
• namorada = girlfriend
• namorar = to date / to be in a romantic relationship

So minha namorada is the standard way to say my girlfriend.

They are related, but not the same.

• apresentar = to introduce
• conhecer = to meet / to get to know / to know

So if you bring your girlfriend to your friends for the first time, you introduce her:

• Vou apresentar minha namorada aos meus amigos.

After that, she will meet/get to know them:

• Ela vai conhecer meus amigos.

So apresentar focuses on the act of making the introduction, while conhecer focuses on meeting or becoming acquainted.

For a repeated, habitual meaning, Portuguese normally uses the plural:

• aos sábados = on Saturdays

So compare:

• No sábado, vou apresentar minha namorada aos meus amigos.
  = on Saturday / this Saturday

• Aos sábados, eu saio com meus amigos.
  = on Saturdays, I go out with my friends

So no sábado is usually a specific Saturday, while aos sábados is habitual.