Você sugere viajar no sábado, mas eu prefiro adiar o passeio para domingo.

Because você takes the third-person singular verb form in Brazilian Portuguese.

So:

• você sugere
• ele sugere
• ela sugere

Even though você means you, grammatically it behaves like he/she for verb endings.

If you used tu instead, some varieties would say tu sugeres.

In Portuguese, the infinitive usually appears by itself. There is no separate word that works exactly like English to in to travel or to postpone.

So:

• sugere viajar = suggests traveling / suggests that someone travel
• prefiro adiar = I prefer to postpone

This is very normal after many verbs in Portuguese.

No is a contraction of:

• em = in / on / at
• o = the

So:

• em + o = no

Literally, no sábado is something like on the Saturday, but in natural English we just say on Saturday.

This happens because days of the week normally use the article in Portuguese:

• o sábado
• o domingo

In Portuguese, days of the week are normally written in lower-case.

So:

• sábado
• domingo
• segunda-feira

This is different from English, where Saturday and Sunday are capitalized.

Because adiar para domingo means to move/postpone something to Sunday.

Here, para shows the new target day for the event.

• adiar o passeio para domingo = postpone the outing to Sunday

If you said no domingo, that would sound more like you are simply locating something on Sunday, not emphasizing the idea of rescheduling it to that day.

Yes, mas prefiro is possible.

The pronoun eu is included for contrast or emphasis:

• Você sugere...
• mas eu prefiro...

It helps highlight the difference between your suggestion and my preference.

Portuguese often drops subject pronouns, but speakers keep them when they want clearer contrast.

Adiar means to postpone, to put off, or to delay until later.

In this sentence:

• adiar o passeio para domingo = postpone the outing until Sunday / move it to Sunday

It usually suggests that the event is still going to happen, just later than originally planned.

Not exactly.

Passeio usually means:

• an outing
• a leisure trip
• a walk
• a casual visit or excursion

Viagem usually means:

• a trip
• travel
• a journey

So passeio often sounds lighter or more recreational than viagem.

In this sentence, the speaker talks about traveling on Saturday, but then says they would rather postpone the outing/trip to Sunday. The words are related, but not perfect synonyms.

Because Portuguese often uses definite articles more than English does, especially when referring to something specific and already understood in the conversation.

So o passeio means:

• the outing
• the trip

Saying just adiar passeio would sound less natural in this context.

Yes. The verbs are in the present tense:

• sugere
• prefiro

That is normal, because the sentence is describing a current suggestion and a current preference about a future plan.

English does something similar:

• You suggest Saturday, but I prefer Sunday.

Yes. That version is also correct.

Compare:

• Você sugere viajar no sábado
• Você sugere que viajemos no sábado

The second version is a bit more explicit because it uses que viajemos = that we travel.

The first version, with the infinitive viajar, is very natural and common in everyday Portuguese.

Yes. Mas means but.

So the structure is:

• Você sugere... = You suggest...
• mas eu prefiro... = but I prefer...

It introduces a contrast between two ideas, just like but in English.