Segundo o orçamento pessoal, a poupança não diminuiu.

Here segundo means according to, not second.

So:

• Segundo o orçamento pessoal = According to the personal budget

Portuguese segundo can have different meanings depending on context:

• o segundo capítulo = the second chapter
• segundo o relatório = according to the report

In this sentence, it is a preposition introducing the source of information.

Portuguese usually uses the definite article here before a specific noun:

• segundo o relatório
• segundo a pesquisa
• segundo o orçamento pessoal

So o means the, and the phrase sounds natural because it refers to a specific budget: the personal budget.

Leaving the article out would sound unusual in standard Portuguese in this sentence.

In Portuguese, adjectives usually come after the noun.

So:

• orçamento pessoal = personal budget
• conta bancária = bank account
• economia doméstica = household economy

English often puts adjectives before the noun, but Portuguese normally puts them after.

Poupança usually means savings or saved money.

Depending on context, it can also mean:

• savings in general
• the amount someone has saved
• in Brazil, sometimes a savings account (conta poupança or simply poupança in some contexts)

In this sentence, a poupança não diminuiu most naturally means the savings did not decrease.

Because Portuguese and English do not always package ideas the same way.

In English, savings is often a plural-looking noun used for money saved. In Portuguese, the usual word is singular:

• a poupança
• minha poupança
• a poupança da família

So even though the English translation may use savings, Portuguese uses a singular noun.

Não is the normal Portuguese word for not, and it usually comes before the verb.

So:

• não diminuiu = did not decrease
• não mudou = did not change
• não cresceu = did not grow

This is the standard way to negate a clause in Portuguese.

Diminuiu is the preterite form of diminuir.

It means something like:

• decreased
• went down
• did decrease

In this sentence, because of não, it becomes did not decrease.

Conjugation of diminuir in the preterite:

• eu diminuí
• você/ele/ela diminuiu
• nós diminuímos
• vocês/eles/elas diminuíram

So diminuiu agrees with a poupança, which is third person singular.

Because the subject is singular:

• a poupança = singular

So the verb must also be singular:

• a poupança diminuiu
• a poupança não diminuiu

If the subject were plural, the verb would change:

• as poupanças não diminuíram = the savings did not decrease

Yes. De acordo com is a very common alternative.

These are both natural:

• Segundo o orçamento pessoal, a poupança não diminuiu.
• De acordo com o orçamento pessoal, a poupança não diminuiu.

A small nuance:

• segundo is a bit more compact and often feels slightly more formal or report-like
• de acordo com is extremely common and clear in many contexts

Both work well.

Diminuir is perfectly natural and means to decrease / to go down / to become less.

Other possible verbs, depending on nuance, include:

• cair = to fall
  • a poupança não caiu
• reduzir = to reduce (more often used when something reduces something else, but can appear in passive-like contexts or formal usage)
• baixar = to go down / lower, but this can sound less precise depending on context

For money, numbers, and amounts, diminuir is a very safe and natural choice.

Yes, in Brazilian Portuguese it sometimes can, depending on context.

For example:

• Vou colocar o dinheiro na poupança.
  = I’m going to put the money in the savings account.

But in your sentence:

• a poupança não diminuiu

the meaning is more likely the savings did not decrease, not specifically the savings account did not decrease.

The broader context decides which meaning is intended.

A little, yes, but the original version is very natural.

Original:

• Segundo o orçamento pessoal, a poupança não diminuiu.

You could also say:

• A poupança não diminuiu, segundo o orçamento pessoal.

That version sounds a bit more like an afterthought or a written report.

What is not natural is moving words around too freely, because Portuguese still has preferred patterns. The original sentence is the most neutral and standard.

In Brazilian Portuguese, diminuiu is pronounced approximately like jee-mee-noo-EE-o or dee-mee-noo-EE-o, depending on accent and how closely you approximate the sounds.

It comes from the verb diminuir. Verbs ending in -uir often create forms with a sequence of vowels:

• diminuir
• diminuiu
• construir
• construiu

That vowel sequence is normal in Portuguese spelling and pronunciation. It may look strange to an English speaker, but it is a regular pattern.

Portuguese often leaves possession more implicit when the context already makes it clear.

So:

• o orçamento pessoal = the personal budget
• meu orçamento pessoal = my personal budget

Both are possible, but o orçamento pessoal is perfectly fine if the speaker is referring to a known personal budget in context.

Portuguese does not always use possessives as often as English does.