Eu não quero cancelar o voo, mas posso adiar o passeio no centro.

Yes, you can usually drop eu in Portuguese.

So Eu não quero cancelar o voo, mas posso adiar o passeio no centro can also be:

Não quero cancelar o voo, mas posso adiar o passeio no centro.

Portuguese often leaves out subject pronouns because the verb form already shows the subject:

• quero = I want
• posso = I can / I may

Keeping eu adds clarity or emphasis. In this sentence, eu sounds natural, but it is not required.

In Portuguese, não normally goes directly before the verb it negates.

So:

• não quero = I do not want
• não posso = I cannot

That is why the sentence says:

Eu não quero cancelar o voo...

If you moved não somewhere else, it would usually sound wrong or change the structure.

Because querer is followed directly by an infinitive in Portuguese.

So you say:

• quero cancelar = I want to cancel
• quero sair = I want to leave
• quero comer = I want to eat

There is no de here.

This is similar to English want to + verb, except Portuguese just uses the infinitive directly after querer.

They are both in the present indicative.

• quero = I want
• posso = I can / I may

In this sentence, the present tense expresses a current situation:

• I don’t want to cancel the flight
• but I can postpone the downtown outing

This is a very common use of the present tense in Portuguese.

They mean different things:

• cancelar = to cancel, meaning something will not happen
• adiar = to postpone / put off / delay, meaning it will happen later

So in the sentence:

• cancelar o voo = cancel the flight completely
• adiar o passeio = postpone the outing/trip/walk to another time

This contrast is important to the meaning of the sentence.

Portuguese uses definite articles very often, more often than English in many contexts.

Here:

• o voo = the flight
• o passeio = the outing / the trip / the walk

In this sentence, the speaker is referring to specific things, so the articles sound natural and expected.

In Portuguese, leaving out the article here would usually sound less natural:

• cancelar o voo
• adiar o passeio

That is the standard way to say it.

Yes, voo is correct.

It comes from the verb voar (to fly) and means flight.

Older spelling used vôo, but modern Brazilian Portuguese spelling writes it as voo without the accent.

So:

• o voo = the flight

The double o is normal in current spelling.

Não has a nasal sound, which is one of the trickier parts for English speakers.

A rough approximation is something like nowng, but that is not exact. The ending is nasal, not a full n sound.

A few tips:

• The ão ending is very common in Portuguese.
• Do not pronounce it like English now.
• The sound comes out through the nose.

Words with the same nasal ending include:

• não
• pão
• irmão

If you are learning Brazilian Portuguese, listening and repeating native audio will help a lot with this sound.

Passeio can mean several related things depending on context:

• an outing
• a stroll
• a walk
• a short trip
• a leisure activity

In this sentence, o passeio no centro most likely means something like:

• the outing downtown
• the trip around downtown
• the walk in the city center

It has a leisure or recreational feeling, not something like a formal journey.

No centro means in the center or, very commonly in Brazilian Portuguese, downtown / in the city center.

No is a contraction:

• em + o = no

So:

• no centro = in the center
• literally: in the + center

Portuguese uses these contractions all the time:

• em + a = na
• de + o = do
• de + a = da

So passeio no centro is the natural way to say outing in the city center / downtown.

It does not have to be repeated.

The sentence says:

Eu não quero cancelar o voo, mas posso adiar o passeio no centro.

After mas, Portuguese often leaves out the subject if it is still clear that it is the same person speaking. Since posso clearly means I can, repeating eu is optional.

You could also say:

Eu não quero cancelar o voo, mas eu posso adiar o passeio no centro.

That version is also correct, but it adds a bit more emphasis to I.

Here, posso most naturally means can in the sense of it is possible / I am able to.

• posso adiar = I can postpone

Depending on context, poder can also express permission, like may, but in this sentence it sounds more like practical possibility:

I don’t want to cancel the flight, but I can postpone the outing downtown.

Yes, absolutely.

Both are correct:

• mas posso adiar...
• mas eu posso adiar...

The version with eu is a little more explicit or emphatic. The version without eu is slightly more natural in many everyday contexts because Portuguese often drops subject pronouns when the meaning is clear.

It can mean both, depending on context.

• centro = center
• in city contexts, very often downtown or city center

So no centro here most likely means:

• downtown
• in the city center

That is a very common use in Brazilian Portuguese.