Podemos descansar, desde que terminemos o relatório hoje.

Here, desde que means as long as, provided that, or on condition that.

So the sentence means something like:

• We can rest, as long as we finish the report today.

Be careful: desde que can also mean since in other contexts, depending on the sentence. In this example, it clearly introduces a condition, not a time starting point.

For example:

• Desde que chegaste, tudo mudou. = Since you arrived, everything changed.
• Podemos sair, desde que acabemos isto. = We can leave, provided that we finish this.

Because desde que expressing a condition normally requires the subjunctive in Portuguese.

So:

• terminemos = present subjunctive
• terminamos = present indicative

In English, learners often expect a normal present tense after if / as long as, but Portuguese often uses the subjunctive after expressions of condition, uncertainty, desire, emotion, and similar ideas.

Compare:

• Terminamos o relatório hoje. = We finish / are finishing the report today.
  This is a statement.
• Podemos descansar, desde que terminemos o relatório hoje.
  This is not stating a fact; it gives a condition. That is why the subjunctive appears.

Terminemos is the present subjunctive, 1st person plural of terminar.

So it means:

• that we finish
• that we may finish

In this sentence, English usually would not translate it with that, but grammatically that is the idea behind it.

A quick conjugation of the present subjunctive of terminar:

• eu termine
• tu termines
• ele/ela/você termine
• nós terminemos
• vós termineis
• eles/elas/vocês terminem

Because after poder (can / to be able to), Portuguese normally uses the infinitive of the main verb.

So:

• Podemos descansar = We can rest

This is exactly parallel to English:

• We can rest
• not We can we rest

Other examples:

• Posso sair. = I can leave.
• Podem entrar. = They can come in.
• Podemos começar. = We can begin.

Portuguese often leaves out subject pronouns when the verb ending already shows who the subject is.

Here:

• podemos already tells us the subject is we
• terminemos also matches we

So Podemos descansar... naturally means We can rest...

You could say:

• Nós podemos descansar...

but it is usually unnecessary unless you want emphasis, contrast, or clarity.

For example:

• Nós podemos descansar, mas eles têm de continuar.
  = We can rest, but they have to continue.

Portuguese uses definite articles more often than English.

So o relatório literally means the report, and in many cases Portuguese sounds more natural with the article where English might sometimes omit it.

In this sentence, the speaker is probably referring to a specific report already known to both people:

• terminemos o relatório hoje = finish the report today

Without the article, relatório would usually sound incomplete or less natural here.

Yes, you often can, but the meaning and structure are a bit different.

• desde que terminemos o relatório hoje = provided that / as long as we finish the report today
• se terminarmos o relatório hoje = if we finish the report today

Both can work, but desde que usually sounds more explicitly conditional, like a requirement that must be met.

Also notice the verb form changes:

• after desde que (conditional meaning), you normally use the subjunctive: terminemos
• after se referring to a future condition, Portuguese often uses the future subjunctive: terminarmos

So:

• Podemos descansar, desde que terminemos o relatório hoje.
• Podemos descansar, se terminarmos o relatório hoje.

Both are possible, but they are not built in exactly the same way.

Because different conjunctions trigger different verb forms.

In this sentence:

• desde que
  • condition → usually takes the present subjunctive
• se
  • future condition → usually takes the future subjunctive

So:

• desde que terminemos = correct
• se terminarmos = correct

But:

• desde que terminarmos = normally not the expected structure here

This is an important pattern in Portuguese and can feel strange to English speakers, because English often uses the same plain present form in several of these situations.

Yes. Hoje is flexible, although the original sentence is very natural.

Original:

• Podemos descansar, desde que terminemos o relatório hoje.

Other possible placements:

• Hoje, podemos descansar, desde que terminemos o relatório.
• Podemos hoje descansar, desde que terminemos o relatório.
• Podemos descansar hoje, desde que terminemos o relatório.

However, the position changes the emphasis slightly.

• ...o relatório hoje emphasizes that the report must be finished today
• Podemos descansar hoje... emphasizes today as the day of resting

So the original version is a good choice if the important time reference is the finishing of the report.

The comma is very natural here because the sentence has a main clause followed by a subordinate conditional clause:

• Podemos descansar, desde que terminemos o relatório hoje.

In practice, you will often see this comma, especially in careful writing.

Without the comma, the sentence would still usually be understandable:

• Podemos descansar desde que terminemos o relatório hoje.

But the comma helps separate the main idea from the condition and makes the sentence easier to read.

This sentence works in both European Portuguese and Brazilian Portuguese.

The grammar is standard in both:

• Podemos descansar
• desde que terminemos
• o relatório hoje

A few pronunciation differences would exist between Portugal and Brazil, but the sentence itself is perfectly normal in both varieties.

For a learner of Portuguese from Portugal, the main thing to notice is the grammar:

• omission of nós
• poder + infinitive
• desde que + subjunctive