Na terça-feira, eu faço a matrícula online para começar o curso em setembro.

Yes. Na terça-feira means on Tuesday.

It is made up of:

• em = in/on
• a terça-feira = Tuesday

When em + a combine, they become na.

So:

• na terça-feira = on Tuesday

In Portuguese, days of the week are often used with the article:

• na segunda-feira = on Monday
• na terça-feira = on Tuesday

Depending on context, na terça-feira can mean:

• on Tuesday in general
• this/next Tuesday, if the situation makes that clear

In standard Portuguese, the normal full name is terça-feira.

The weekdays are:

• segunda-feira = Monday
• terça-feira = Tuesday
• quarta-feira = Wednesday
• quinta-feira = Thursday
• sexta-feira = Friday

The word feira is part of the official weekday name. In casual speech, some people may shorten it, but learners should use the full form, especially in Portugal.

Because the weekday names are written as compound words with a hyphen:

• segunda-feira
• terça-feira
• quarta-feira, etc.

This is just the standard spelling, so it is something you should learn as a fixed form.

Portuguese often uses the present tense to talk about a planned or scheduled future action, especially when there is a clear time expression.

Here, Na terça-feira makes the future time clear, so eu faço can mean:

• I do it on Tuesday
• I’m doing it on Tuesday
• I will do it on Tuesday

This is very natural in Portuguese, just as English sometimes says:

• I’m enrolling on Tuesday instead of
• I will enroll on Tuesday

Not always. Portuguese usually allows you to omit the subject pronoun when the verb ending already shows who the subject is.

So both are possible:

• Na terça-feira, eu faço a matrícula online...
• Na terça-feira, faço a matrícula online...

Both are correct.

Including eu can:

• add emphasis
• make the subject extra clear
• sound slightly more explicit

Faço is the 1st person singular of fazer:

• fazer = to do / to make

So literally, eu faço a matrícula means something like:

• I do the enrollment/registration

In more natural English, you would usually translate the whole phrase as:

• I enroll
• I register
• I complete the enrollment

This is a good example of where the literal verb and the natural English translation are not exactly the same.

Here, a matrícula means the enrollment / the act of registering, especially for a school, course, or university.

In context:

• fazer a matrícula = to enroll / to register

A useful point for learners: in Portuguese, matrícula can also refer to related ideas depending on context, but in education it very commonly means enrollment/registration.

In Portugal, you may also hear inscrição in some contexts. Very roughly:

• inscrição often means registration/sign-up
• matrícula often refers more specifically to formal enrollment, especially in education

In this sentence, matrícula is perfectly natural.

Because in Portuguese, nouns often appear with an article where English would not use one.

So:

• fazer a matrícula = literally to do the enrollment

This is the normal structure. Leaving out the article here would usually sound unnatural.

This is a common pattern for English speakers to get used to:

• fazer a reserva = make the reservation
• tomar o pequeno-almoço = have breakfast
• apanhar o autocarro = take the bus

Because online is describing how the enrollment is done.

So:

• faço a matrícula online = I do the enrollment online

This word order is very natural in Portuguese. You are likely to see online after the noun or after the verb phrase.

For example:

• Compro os bilhetes online. = I buy the tickets online.
• Fiz a inscrição online. = I registered online.

Yes. Pela internet is also possible and clearly understood.

Compare:

• faço a matrícula online
• faço a matrícula pela internet

Both are natural. Online is very common in modern Portuguese, including in Portugal.

Para here means in order to or to, expressing purpose.

So:

• para começar o curso = to start the course / in order to start the course

The structure is:

• para + infinitive

Examples:

• Estudo para passar no exame. = I study to pass the exam.
• Poupo dinheiro para viajar. = I save money to travel.

In your sentence, the idea is:

• I complete the enrollment online so that I can start the course in September.

Because começar can take a direct object.

So:

• começar o curso = to start the course

That is the normal structure here.

You would not normally say começar no curso for this meaning.

Compare:

• Vou começar o livro. = I’m going to start the book.
• Ela começou o trabalho cedo. = She started the work early.

Because em is the normal preposition used with months.

So:

• em setembro = in September

Other examples:

• em janeiro = in January
• em agosto = in August
• em 2026 = in 2026

This is quite similar to English in September.

Yes, but in this context it most naturally sounds like a plan.

That is because the sentence includes:

• a specific time: Na terça-feira
• a purpose: para começar o curso em setembro

So the most likely meaning is a scheduled future action:

• On Tuesday, I’m enrolling online to start the course in September.

Without more context, it is less likely to be understood as a repeated habit.

Yes, it sounds natural and correct.

A native speaker might also say slightly different versions, such as:

• Na terça-feira, faço a matrícula online para começar o curso em setembro.
• Na terça, faço a matrícula online para começar o curso em setembro.
  (more informal)
• Na terça-feira, vou fazer a matrícula online para começar o curso em setembro.
  (more explicitly future)

All of these are natural, but your original sentence is perfectly good European Portuguese.

A fairly literal breakdown is:

• Na terça-feira = On Tuesday
• eu faço = I do / I make
• a matrícula = the enrollment / the registration
• online = online
• para começar = to start / in order to start
• o curso = the course
• em setembro = in September

So very literally:

• On Tuesday, I do the enrollment online to start the course in September.

More natural English:

• On Tuesday, I enroll online to start the course in September.
• On Tuesday, I register online so I can start the course in September.