Se eu continuar a tossir assim, amanhã vou ficar ainda mais rouco.

Because after se when you mean if about a possible future situation, Portuguese uses the future subjunctive.

So:

• Se eu continuar = If I continue
• not Se eu continuarei

This is very common in Portuguese:

• Se eu tiver tempo, vou contigo. = If I have time, I’ll go with you.
• Se ele vier, falamos com ele. = If he comes, we’ll speak to him.

The future subjunctive often looks like the personal infinitive in many verbs, so continuar here may look simple, but grammatically it is the correct form for this if clause.

In European Portuguese, continuar a + infinitive is the normal way to say to keep doing something or to continue doing something.

So:

• continuar a tossir = to keep coughing / to continue coughing

This a is part of the structure. Similar examples:

• continuar a falar = to keep talking
• continuar a chover = to keep raining
• começar a trabalhar = to start working

A native English speaker may expect something like continuar tossindo because of Brazilian Portuguese patterns, but in Portugal, continuar a + infinitive is much more natural.

In European Portuguese, that sounds non-standard or strongly Brazilian. In Portugal, the usual form is:

• continuar a tossir

More broadly, European Portuguese normally prefers a + infinitive where Brazilian Portuguese often uses the gerund:

• EP: estou a estudar
• BP: estou estudando

So for Portugal Portuguese, continuar a tossir is the form learners should use.

Both are possible, but vou ficar is much more common in everyday speech.

• vou ficar = I’m going to become / I’ll become
• ficarei = I will become

In conversation, European Portuguese often prefers ir + infinitive for the future, just like English often prefers I’m going to... or even I’ll...

So:

• amanhã vou ficar ainda mais rouco sounds natural and conversational
• amanhã ficarei ainda mais rouco sounds more formal, literary, or less conversational

Ficar often means to become or to get when it is followed by an adjective.

So:

• ficar rouco = to become hoarse
• literally, something like to get hoarse

Other common examples:

• ficar cansado = to get tired
• ficar doente = to get sick
• ficar triste = to become sad

So in this sentence, vou ficar ainda mais rouco means I’ll get even hoarser.

Ainda mais means even more.

So:

• mais rouco = hoarser / more hoarse
• ainda mais rouco = even hoarser

It adds emphasis. The speaker is saying their voice is already affected, and if the coughing continues, it will get worse.

Other examples:

• ainda mais difícil = even more difficult
• ainda mais caro = even more expensive
• ainda mais cansado = even more tired

Because the adjective must agree with the person speaking.

• rouco = masculine singular
• rouca = feminine singular

So if a man is speaking, he says:

• vou ficar ainda mais rouco

If a woman is speaking, she says:

• vou ficar ainda mais rouca

This agreement is very important in Portuguese.

Yes, amanhã can move around a bit. Portuguese word order is flexible here.

The original sentence:

• Se eu continuar a tossir assim, amanhã vou ficar ainda mais rouco.

Also possible:

• Se eu continuar a tossir assim, vou ficar ainda mais rouco amanhã.
• Amanhã, se eu continuar a tossir assim, vou ficar ainda mais rouco.

The original placement sounds very natural. Putting amanhã before vou ficar helps frame the second part clearly: tomorrow, I’ll be even hoarser.

Assim here means like this or like that, depending on context. In this sentence it means something like:

• coughing like this
• coughing in this way
• coughing this much

So:

• Se eu continuar a tossir assim = If I keep coughing like this

It refers to the current way or intensity of the coughing.

Portuguese usually does not need a separate word for then in this kind of conditional sentence.

English can say:

• If I keep coughing like this, then I’ll be even hoarser tomorrow.

But in both English and Portuguese, then is often optional. Portuguese normally just says:

• Se eu continuar a tossir assim, amanhã vou ficar ainda mais rouco.

That is completely natural.

Mostly yes, but it has a small spelling change in some forms to preserve pronunciation.

Infinitive:

• tossir = to cough

Examples:

• eu tusso = I cough
• tu tosses = you cough
• ele/ela tosse = he/she coughs

The o changes to u in eu tusso, which learners often notice. But in continuar a tossir, the verb is in the infinitive, so you just use the base form tossir.

It is specifically about becoming or ending up more hoarse.

That comes from ficar, which often expresses a change of state:

• ficar rouco = become hoarse / get hoarse

So the idea is not only how the person sounds right now, but that their condition will worsen by tomorrow.

Yes, it could be omitted:

• Se continuar a tossir assim, amanhã vou ficar ainda mais rouco.

Portuguese often drops subject pronouns because the verb form usually makes the subject clear. However, eu may be included for clarity, emphasis, or rhythm.

So both are natural:

• Se eu continuar a tossir assim...
• Se continuar a tossir assim...

Including eu makes the subject slightly more explicit.