O professor pediu um agrafador, mas eu só tinha um clip e um agrafo na mochila.

These three words are easy to mix up:

• agrafador = stapler
• agrafo = staple
• clip = paper clip

So the sentence contrasts the thing the teacher wanted (agrafador) with the small office items the speaker actually had (um clip e um agrafo).

Because the sentence uses two different past ideas:

• pediu is the preterite of pedir and shows a completed action: the teacher asked for something.
• tinha is the imperfect of ter and shows a background situation or ongoing state: at that moment, I only had those items.

This is very common in Portuguese narrative: a completed event in the preterite plus background information in the imperfect.

Here it means to ask for or to request.

That is important because English uses ask for both ideas, but Portuguese often separates them:

• pedir = to ask for / request
• perguntar = to ask a question

So O professor pediu um agrafador means the teacher requested a stapler, not that he asked a question.

Yes, it could.

Portuguese often drops subject pronouns because the verb already shows the person. Tinha already tells you it is I had.

So both are possible:

• mas eu só tinha...
• mas só tinha...

Including eu adds a bit of emphasis or contrast, especially after mas: but I only had...

Here só means only.

So eu só tinha means I only had.

Placing só before the verb is very natural in European Portuguese. You may also hear eu tinha só um clip..., which puts the focus more directly on the items that follow. Both are possible, but eu só tinha... is a very normal way to say it.

Also, note that só can sometimes mean alone, but not in this sentence.

Because em + a contracts to na.

This kind of contraction is standard in Portuguese:

• em + o = no
• em + a = na
• em + os = nos
• em + as = nas

So na mochila is the normal form. em a mochila would sound wrong in standard Portuguese.

Because Portuguese does not always need the possessive when ownership is obvious from the context.

So na mochila can naturally mean in the backpack or, depending on context, in my backpack.

If the speaker wants to be more explicit, they can say na minha mochila. Both are possible, but the shorter version is often enough when everyone knows whose backpack is being talked about.

Repeating um makes it clear that these are two separate items: one paper clip and one staple.

Portuguese normally repeats the article in this kind of structure, especially when listing singular countable nouns. It sounds natural and precise:

• um clip e um agrafo

If you left out the second um, it would sound less natural here.

Because grammatical gender in Portuguese belongs to the noun itself, and these nouns are conventionally masculine.

That is why they take um:

• um agrafador
• um clip
• um agrafo

This does not mean the objects are somehow “male”; it is just how the nouns are classified in Portuguese. As a learner, it is best to memorize nouns together with their article.

Yes. In Portugal, clip is a normal everyday word for paper clip.

It is a borrowing from English, but it behaves like a regular Portuguese noun:

• um clip
• dois clips

So even though it looks English, it is completely natural in this sentence.