Às vezes, eu engano-me no acento dessa palavra e ponho um ponto final onde devia haver uma vírgula.

Às vezes means sometimes.

The à in às is the contraction of a + as, written with a grave accent: à / às. In this fixed expression, Portuguese uses às before vezes.

So:

• às = to the / at the in this kind of expression
• vezes = times

Literally, it is close to at times.

Because it starts the sentence, it is capitalized: Às vezes.

Because Às vezes is an introductory adverbial expression, and it is very common to separate that kind of opening phrase with a comma.

So Às vezes, eu engano-me... sounds natural and well-punctuated.

In many cases, especially in shorter sentences, the comma may be omitted, but using it here is completely normal.

Not strictly. Portuguese often drops subject pronouns because the verb ending already shows the person.

So both of these are possible:

• Às vezes, eu engano-me...
• Às vezes, engano-me...

Including eu can add a little emphasis, contrast, or clarity. It is not wrong at all; it just is not always required.

This is a very important European Portuguese pattern.

The verb here is enganar-se, and in affirmative main clauses, European Portuguese normally puts the object/reflexive pronoun after the verb:

• engano-me
• levanto-me
• chamo-me

This is called enclisis.

So in Portugal, eu engano-me is the usual order.

In Brazilian Portuguese, eu me engano is much more common. A learner of European Portuguese should get used to the pronoun-after-the-verb pattern in sentences like this.

Here enganar-se means to make a mistake, to be mistaken, or to get something wrong.

So eu engano-me no acento dessa palavra means that the speaker makes mistakes with the accent of that word.

It does not mean I deceive myself here, even though in other contexts enganar can relate to deceiving or tricking.

They are contractions, and contractions like these are very common in Portuguese.

• no = em + o
• dessa = de + essa

So:

• no acento = in/on the accent
• dessa palavra = of that word

These contractions are normal and expected. Portuguese usually does not say em o or de essa in standard usage here.

In Portuguese, acento can refer to different things depending on context:

• a spoken accent or way of speaking
• a written accent mark
• the stress/accentuation of a word

In this sentence, it clearly refers to the accent of the word, meaning its written accentuation or accent mark, not someone’s foreign accent.

Yes. Ponho is the first person singular present of pôr, which means to put.

So:

• eu ponho = I put
• tu pões
• ele/ela põe

This verb is irregular, so the form is not predictable from the infinitive in the way many regular verbs are.

In the sentence, ponho fits because the speaker is describing something that happens sometimes, so the present tense is natural.

Ponto final means full stop in British English or period in American English.

In Portugal, ponto final is a very clear and standard way to refer to that punctuation mark specifically.

Sometimes ponto may also be understood from context, but ponto final is more precise and avoids ambiguity, since ponto can also mean point, dot, or other kinds of mark.

This part literally means something like where there should be a comma.

A few things are happening here:

• onde = where
• devia = should / was supposed to
• haver = to exist / to be there
• uma vírgula = a comma

So the speaker is saying they put a full stop in a place where a comma ought to be.

Using onde is natural because the sentence is talking about a position in the written text.

All three are possible in some contexts, but they do not sound exactly the same.

• deve haver = stronger, more direct, more like there must be / there should be
• devia haver = very common, natural, slightly softer
• deveria haver = also correct, often a bit more formal or explicit

In everyday Portuguese, devia is often used where English would use should. So onde devia haver uma vírgula sounds very natural.

Here haver is being used in its existential sense, like there is / there are in English.

So:

• há uma vírgula
• há duas vírgulas

When haver has this existential meaning, it is impersonal, so it stays in the singular.

That means even with a plural noun, standard Portuguese still uses singular haver:

• onde devia haver duas vírgulas
• not onde deviam haver duas vírgulas

This is a very common point for learners.

This is about the demonstratives este/esse/aquele and their forms.

• desta palavra = of this word
• dessa palavra = of that word

In practice, especially in modern usage, the distinction can depend on perspective and context. Here dessa palavra suggests a word that has already been mentioned or is being referred to as that word rather than this word here.

If the speaker were pointing to the word right in front of them, desta palavra could also make sense in another context. But in the sentence you gave, dessa palavra is perfectly natural.