Assim que a reunião terminar, vou falar com a gerente.

Assim que means as soon as.

It introduces an action that will happen immediately after another one. So the idea is:

• first, the meeting ends
• right after that, the speaker will talk to the manager

It is a very common way to connect two future actions in Portuguese.

Because after expressions like assim que, Portuguese normally uses the future subjunctive when talking about a future event.

So:

• Assim que a reunião terminar... = As soon as the meeting ends / has ended...

Using termina here would sound more like a habitual or general statement in standard grammar, not the normal way to talk about a specific future event.

Using terminará after assim que is not the usual structure. In Portuguese, after conjunctions like quando, assim que, logo que, se, and depois que, future meaning is often expressed with the future subjunctive, not the simple future.

It looks like the infinitive, but in this sentence it is actually the future subjunctive form.

For regular -ar verbs, the future subjunctive often has the same form as the infinitive:

• infinitive: terminar
• future subjunctive: quando eu terminar, quando você terminar, quando a reunião terminar

So the form is identical, but the function is different.

Both are correct, but vou falar is much more common in everyday Brazilian Portuguese.

• vou falar = I’m going to talk / I will talk
• falarei = I will talk

In Brazil, the ir + infinitive future is very natural in speech and informal writing.
Falarei is grammatically fine, but it can sound more formal, more written, or less conversational.

So this sentence sounds very natural:

• Assim que a reunião terminar, vou falar com a gerente.

Because Portuguese often drops subject pronouns when the verb already makes the subject clear.

• vou already shows I
• so (eu) vou falar and vou falar both mean the same thing

Including eu is possible:

• Assim que a reunião terminar, eu vou falar com a gerente.

That version may sound slightly more emphatic, but the version without eu is completely normal.

Yes. That would also be correct.

The difference is mainly nuance:

• quando = when
• assim que = as soon as

So assim que emphasizes that the second action will happen immediately after the first one.

Compare:

• Quando a reunião terminar, vou falar com a gerente.
  = When the meeting ends, I’ll talk to the manager.

• Assim que a reunião terminar, vou falar com a gerente.
  = As soon as the meeting ends, I’ll talk to the manager.

Both work, but assim que is more specific.

Yes, both can be possible, but falar com is the most natural choice if you mean talk with / talk to someone, especially in a conversational sense.

• falar com a gerente = talk with/to the manager
• falar para a gerente = speak to the manager / tell the manager

Very roughly:

• com often suggests interaction or conversation
• para can sound a little more one-directional, depending on context

In this sentence, falar com a gerente sounds very natural because the speaker is probably going to have a conversation with her.

Because both nouns are being treated as specific.

• a reunião = the meeting
• a gerente = the manager

If you said uma reunião, that would mean a meeting in a non-specific sense.
If you said uma gerente, that would mean a manager rather than the manager.

So this sentence suggests that both speaker and listener know which meeting and which manager are being referred to.

Yes. In this sentence, a gerente refers to a female manager.

The noun gerente usually has the same form for both genders. The article tells you whether the person is male or female:

• o gerente = the male manager
• a gerente = the female manager

So the noun itself does not change here; the article does the work.

Yes, absolutely. That is a very natural sentence too.

• Assim que a reunião terminar, vou falar com a gerente.
• Vou falar com a gerente assim que a reunião terminar.

Both mean the same thing.

The main difference is focus:

• starting with Assim que... puts early attention on the timing
• starting with Vou falar... puts early attention on the main action

Also, when the assim que clause comes first, a comma is normally used.
When it comes second, the comma is often omitted.

The structure is:

Assim que + subject + future subjunctive, main clause in the future

So in this sentence:

• Assim que = conjunction
• a reunião = subject of the first clause
• terminar = future subjunctive verb
• vou falar com a gerente = main clause

A very literal breakdown is:

• Assim que = as soon as
• a reunião = the meeting
• terminar = ends
• vou falar = I am going to talk / I will talk
• com a gerente = with/to the manager

Yes. Several common expressions can introduce a future event and are often followed by the future subjunctive:

• quando = when
• logo que = as soon as
• depois que = after
• assim que = as soon as

Examples:

• Quando a reunião terminar, vou sair.
• Logo que a reunião terminar, vou sair.
• Depois que a reunião terminar, vou sair.

Among these, assim que and logo que strongly suggest immediacy.
In everyday Brazilian Portuguese, assim que is very common and natural.