Eu vou falar com você à noite.

Yes. Portuguese often allows the subject pronoun to be omitted, so Vou falar com você à noite is also perfectly natural.

Eu is included here for one of these common reasons:

• to make the subject extra clear
• to add emphasis, like I will talk to you tonight
• simply because speakers sometimes say it even when it is not necessary

In everyday Brazilian Portuguese, both versions are common:

• Eu vou falar com você à noite.
• Vou falar com você à noite.

Vou falar is the very common ir + infinitive future construction.

• vou = I go / I am going from the verb ir
• falar = to speak / to talk

Together, vou falar means I am going to speak / I will speak.

This is one of the most common ways to talk about the future in Brazilian Portuguese. It often sounds more natural in conversation than the simple future form.

Yes. Falarei com você à noite is grammatically correct.

But in Brazilian Portuguese:

• vou falar is more common in everyday speech
• falarei can sound more formal, more written, or sometimes more emphatic

So:

• Eu vou falar com você à noite. = very natural, conversational
• Falarei com você à noite. = correct, but less common in ordinary spoken Brazilian Portuguese

Because falar usually uses the preposition com when it means to talk to / speak with someone.

So:

• falar com alguém = to talk to someone

Examples:

• Vou falar com ele. = I’m going to talk to him.
• Ela falou com a professora. = She spoke with the teacher.

If you say falar você, that is not correct for this meaning.

Sometimes, yes, but the structure changes a little.

• Vou falar com você = I’m going to talk to you
• Vou te falar often means I’m going to tell you or I’m going to say something to you

So they are close, but not always identical.

A useful distinction is:

• falar com você = emphasize the conversation or speaking with the person
• te falar = often emphasize telling or saying something to the person

For the exact sentence you were given, falar com você is the most direct match.

Yes, it could, depending on region and situation.

In Brazil:

• você is very common in many regions
• tu is also used in some regions, but usage varies a lot

So you might hear:

• Eu vou falar com você à noite.
• Eu vou falar contigo à noite.
• Eu vou falar com tu à noite. in some regional speech, though this is not standard grammar

A more traditionally standard version with tu would be:

• Eu vou falar contigo à noite.

For learners, você is usually the safest and most widely understood choice in Brazil.

À noite means at night, in the evening, or tonight, depending on context.

The à is a contraction of:

• a = the preposition
• a = the feminine article the

So:

• a + a = à

The accent is not just a stress mark here. It shows this contraction, called crase in Portuguese.

You also see this in phrases like:

• à tarde = in the afternoon
• à esquerda = to the left

They are very similar, and in many situations both are used in Brazil.

• à noite is often taught as the more standard textbook expression
• de noite is also very common in everyday speech

Examples:

• Eu estudo à noite.
• Eu estudo de noite.

Both can mean I study at night / in the evening.

In your sentence, à noite sounds completely natural and standard.

It depends on context.

In Eu vou falar com você à noite, most people would understand it as tonight if you are talking about a specific upcoming time.

But à noite by itself can also mean at night / in the evening more generally.

Compare:

• Eu trabalho à noite. = I work at night / in the evening.
• Eu vou falar com você à noite. = I’ll talk to you tonight.

The future context vou falar makes the specific-time reading very natural.

Yes, a little.

The basic order here is very natural:

• Eu vou falar com você à noite.

But Portuguese allows some flexibility, especially to emphasize time or contrast:

• À noite, eu vou falar com você.
• Eu vou, à noite, falar com você. though this sounds more marked or literary
• Vou falar com você à noite.

The original order is the most neutral and natural one for everyday use.

A simple approximate pronunciation is:

eh-ooh voh fah-LAR kohng voh-SEH ah NOY-chee

A few helpful notes:

• Eu often sounds like eh-ooh or even more compressed in fast speech
• vou rhymes roughly with English go without the final glide being too strong
• falar has stress on the last syllable: fa-LAR
• você has stress on the last syllable: vo-SE
• noite sounds roughly like NOY-chee in most of Brazil
• com você is often pronounced smoothly together in natural speech

It is neutral and very natural.

• você is common in everyday Brazilian Portuguese
• the structure vou falar is conversational and standard
• nothing in the sentence is especially formal or especially slangy

So this sentence works well in many normal situations. If you wanted something more formal, you might change the pronoun depending on who you are addressing, but the sentence as it stands is perfectly normal Brazilian Portuguese.