Se avançarmos com calma, vamos terminar o projeto hoje.

Because after se when you are talking about a future possibility or condition, Portuguese normally uses the future subjunctive.

So:

• Se avançarmos com calma = If we move ahead / proceed calmly
• not Se avançamos... in this meaning

This is one of the most common patterns in Portuguese:

• Se tivermos tempo, vamos sair. = If we have time, we’ll go out.
• Se fores cedo, apanhas o comboio. = If you go early, you catch the train.

For avançar, the future subjunctive form for nós is avançarmos.

Here avançar does not necessarily mean a literal physical advance. It means something like:

• to move forward
• to make progress
• to proceed

So Se avançarmos com calma suggests:

• If we keep moving forward steadily
• If we proceed calmly
• If we make progress without rushing

In work or project contexts, avançar is very common in Portuguese.

Com calma literally means with calm, but in natural English it usually means:

• calmly
• without rushing
• taking it easy
• steadily

In this sentence, it suggests doing the work in a careful, controlled way, not in a panicked or hurried way.

You also hear com calma very often in everyday Portuguese:

• Fala com calma. = Speak calmly.
• Vamos com calma. = Let’s take it easy / let’s not rush.

Vamos terminar is the very common ir + infinitive future, equivalent to we’re going to finish or simply we’ll finish.

So:

• vamos terminar o projeto hoje
• terminaremos o projeto hoje

Both can mean we will finish the project today.

The difference is mostly about style and tone:

• vamos terminar sounds more natural and common in everyday speech
• terminaremos is a more synthetic future and can sound slightly more formal, written, or definite depending on context

In modern spoken Portuguese, ir + infinitive is extremely common.

Portuguese often drops subject pronouns because the verb ending already shows who the subject is.

Here:

• avançarmos already shows we
• vamos already shows we

So nós is not necessary.

You could say:

• Se nós avançarmos com calma, vamos terminar o projeto hoje.

But that usually adds emphasis or contrast. In neutral speech, leaving out nós is more natural.

Se here means if. It introduces a condition:

• Se avançarmos com calma = If we proceed calmly

This is a very common structure in Portuguese:

• Se chover, ficamos em casa. = If it rains, we stay home.
• Se puderes, liga-me. = If you can, call me.

So the whole sentence has a clear if ... then ... meaning, even though Portuguese does not need to say then.

The comma separates the conditional clause from the main clause:

• Se avançarmos com calma, = conditional part
• vamos terminar o projeto hoje. = main result

This is standard punctuation when the if-clause comes first.

If you reverse the order, the comma is often not needed:

• Vamos terminar o projeto hoje se avançarmos com calma.

Both versions are correct.

Yes. That is perfectly natural.

The difference is mainly emphasis:

• Se avançarmos com calma, vamos terminar o projeto hoje.
  Focuses first on the condition
• Vamos terminar o projeto hoje se avançarmos com calma.
  Focuses first on the result

Both mean the same thing overall.

Portuguese often uses the definite article where English may or may not use the.

Here o projeto means the project, referring to a specific project that speaker and listener already know about.

Without the article, projeto would usually sound less natural in this sentence unless it were part of a different structure.

So:

• terminar o projeto = finish the project

This use of the article is completely normal in Portuguese.

In practice, hoje is understood mainly with terminar:

• vamos terminar o projeto hoje = we’re going to finish the project today

So the idea is that today is the day of completion.

The sentence does not mainly mean if today we proceed calmly. The position of hoje makes it naturally attach to the finishing of the project.

Yes, it is perfectly natural in European Portuguese.

A European Portuguese learner might especially notice that:

• vamos terminar is very normal in speech
• com calma is a very common everyday expression
• dropping nós is standard and natural

So the sentence sounds idiomatic and normal for Portugal.

This is a good question because avançarmos has the same form as the personal infinitive.

So avançarmos can be:

• future subjunctive in a sentence like this:
  Se avançarmos com calma...
• personal infinitive in other structures, for example:
  É importante avançarmos com calma. = It’s important for us to proceed calmly.

In your sentence, after se referring to a future condition, it is understood as future subjunctive.

Not in the most direct reading of this sentence. Here se means if, because it expresses a condition.

• Se avançarmos com calma, vamos terminar o projeto hoje.
  = If we proceed calmly, we’ll finish the project today.

If the speaker were certain the condition would happen, Portuguese would more naturally use quando:

• Quando avançarmos mais, decidimos o resto.
  = When we move forward more, we’ll decide the rest.

So in your sentence, if is the right interpretation.

Historically, it comes from the verb ir (to go) + infinitive, but in modern Portuguese this structure functions as a future tense expression.

So although word by word it looks like we go to finish, you should understand it as:

• we are going to finish
• or simply we will finish

This is exactly the same kind of idea as in English going to future, though the usage patterns are not always identical.