Depois de pagar o boleto, meu saldo ficou menor do que eu esperava.

Because depois normally takes the preposition de before a verb in the infinitive.

• depois de pagar = after paying
• depois de comer = after eating
• depois de sair = after leaving

So the pattern is:

depois de + infinitive

If a full clause follows, you can also use:

• depois que eu paguei o boleto = after I paid the bill

Both are correct, but depois de + infinitive is very common and compact.

Boleto is short for boleto bancário, a very common Brazilian payment slip. It is used to pay things like:

• utility bills
• online purchases
• school fees
• subscriptions
• rent in some cases

A boleto usually has a barcode, a due date, and an amount to be paid. In English, there is no perfect one-word equivalent, so depending on context it may be translated as:

• bill
• payment slip
• bank slip

So in this sentence, pagar o boleto means paying that bill/payment slip.

In Portuguese, articles are used much more often than in English. So when talking about a specific item, Portuguese usually says:

• pagar o boleto
• abrir a porta
• lavar o carro

Even where English might sound more natural without a strong emphasis on the, Portuguese often includes the article.

So pagar o boleto is the normal way to say pay the bill/payment slip.

Meu saldo means my balance. Portuguese often uses possessives just like English when referring to personal things.

• meu saldo = my balance
• meu cartão = my card
• minha conta = my account

You could sometimes omit the possessive if the context makes it obvious, but meu saldo is completely natural and clear here.

Also note:

• saldo is masculine
• so the possessive is meu, not minha

Here ficou means ended up / became / was left.

The verb ficar often expresses a change of state:

• ficou menor = became smaller
• ficou triste = became sad
• ficou pronto = became ready / got finished

In this sentence, the idea is that after paying the boleto, the balance changed and was now smaller than expected.

Why not the others?

• foi would not sound natural for this kind of result/change here
• estava means was, describing a state, not really the change that happened

So ficou menor is the natural choice because it emphasizes the resulting state after the payment.

Yes. Literally, ficou menor means became smaller or got smaller.

In financial context, it sounds natural in Portuguese to say a balance ficou menor. In English, we might more often say:

• my balance was lower
• my balance ended up lower
• my balance was smaller than I expected

So the literal idea is became smaller, but the best English translation may vary depending on style.

Yes, both menor do que and menor que are used.

• menor do que eu esperava
• menor que eu esperava

Both mean smaller/lower than I expected.

A few notes:

• do que is very common after comparatives like maior, menor, melhor, pior
• que alone is also very common, especially in everyday speech

So menor do que is perfectly correct and sounds natural.

Because the object is understood from context.

In menor do que eu esperava, the idea is:

• smaller than I expected (it to be)

Portuguese often leaves out words that are obvious. A more explicit version could be something like:

• menor do que eu esperava que fosse
• menor do que eu esperava

The shorter version is much more natural in everyday language.

So eu esperava here means I expected with the rest implied.

Because esperava expresses what the speaker was expecting at that time.

The imperfect often describes:

• ongoing mental states
• expectations
• background information
• repeated actions

Here, eu esperava means I was expecting or simply I expected.

Compare:

• eu esperava = I was expecting / I expected
• eu esperei = I waited or sometimes I did expect, depending on context

In this sentence, esperava is the natural tense because it refers to the expectation the speaker had before seeing the final balance.

No, not exactly.

• dinheiro = money in general
• saldo = balance, especially the amount available in an account, card, or similar place

Examples:

• Tenho pouco dinheiro. = I have little money.
• Meu saldo está baixo. = My balance is low.

So meu saldo ficou menor refers specifically to the balance remaining, not just money in a broad sense.

Sometimes, yes, but menor is very natural here.

With financial amounts and balances, Portuguese often uses:

• menor
• mais baixo

Examples:

• meu saldo ficou menor
• meu saldo ficou mais baixo

Both can work, but menor is concise and very common in comparisons like this.

A small nuance:

• menor focuses on smaller in amount
• mais baixo focuses on lower level

In many everyday contexts, the difference is minor.

The opening phrase Depois de pagar o boleto sets the time/context first: After paying the boleto...

This kind of structure is very common in Portuguese, just as in English:

• After paying the bill, my balance...
• Depois de pagar o boleto, meu saldo...

It helps show the sequence of events clearly:

1. first, the boleto was paid
2. then, the balance was lower than expected

You could also change the order:

• Meu saldo ficou menor do que eu esperava depois de pagar o boleto.

But the original version sounds smoother and avoids any ambiguity about what happened first.

The original sentence is already natural. But in casual speech, a Brazilian might also say things like:

• Depois que paguei o boleto, meu saldo ficou menor do que eu esperava.
• Depois de pagar o boleto, meu saldo ficou mais baixo do que eu esperava.
• Depois que eu paguei o boleto, sobrou menos do que eu esperava.

These versions all keep the same basic idea, but the original sentence is absolutely normal and idiomatic in Brazilian Portuguese.