Enquanto o pintor trabalhava, eu segurava a fita adesiva e a chave de fendas.

Enquanto means while and introduces a clause that describes something happening at the same time as another action.

In Enquanto o pintor trabalhava, eu segurava..., the idea is that the painter was working at the same time that I was holding the tools.

It does not require any special verb form by itself here. What matters is the meaning: two ongoing past actions happening simultaneously.

They are both in the imperfect because they describe ongoing or background actions in the past.

• trabalhava = was working / used to work
• segurava = was holding / used to hold

In this sentence, both actions were in progress at the same time, so the imperfect is very natural.

A useful contrast:

• Enquanto o pintor trabalhava, eu segurava a fita adesiva.
  Both actions were ongoing.

• Enquanto o pintor trabalhava, o telefone tocou.
  tocou is preterite because the phone rang as a completed event interrupting the scene.

Yes. In European Portuguese, estar a + infinitive is the normal progressive structure.

So you could say:

Enquanto o pintor estava a trabalhar, eu estava a segurar a fita adesiva e a chave de fendas.

That is grammatically correct, but in this sentence it sounds a bit heavier because the simple imperfect already makes the simultaneous ongoing action clear.

In many cases, European Portuguese prefers the simple imperfect when the context already shows the action was in progress.

Portuguese usually uses the definite article with common nouns when referring to a specific person or thing.

So o pintor means the painter. Leaving out the article would usually sound unnatural here.

This is much more common in Portuguese than in English. English often says the painter, but Portuguese is even more regular about using articles with nouns in this kind of context.

Yes, eu could be left out.

Portuguese often drops subject pronouns because the verb ending already shows the person:

• segurava already tells you it is I or he/she depending context, but here the contrast with o pintor trabalhava makes eu very clear.

So both are possible:

• Enquanto o pintor trabalhava, eu segurava...
• Enquanto o pintor trabalhava, segurava...

Including eu can add clarity or emphasis, especially when contrasting two subjects: the painter and I.

Because Portuguese normally repeats the article before each definite noun in a list.

So:

• a fita adesiva e a chave de fendas

sounds more natural than leaving out the second a.

This is very common in Portuguese:

• o livro e o caderno
• a mesa e a cadeira
• os pais e os filhos

English often avoids repeating the, but Portuguese usually keeps it.

It can mean either, depending on context.

• pintor can be painter in the artistic sense
• pintor can also be painter/decorator in the practical trades sense

In this sentence, because of the tools and work situation, it clearly means a house painter / decorator, not an artist painting a canvas.

Context is what tells you which meaning is intended.

Fita adesiva literally means adhesive tape.

It is a fairly general term, so the exact kind of tape depends on context. In a decorating or DIY situation, it could refer to something like masking tape or another tape used during the job.

In Portugal, you may also hear fita-cola in everyday speech for sticky tape. But fita adesiva is perfectly correct and neutral.

Chave de fendas literally means a slotted screwdriver, that is, a screwdriver for screws with a straight slot.

In many learner translations it may simply appear as screwdriver, but technically it refers to the flat-head type.

If you want to be more specific about other types, you might hear:

• chave Phillips = Phillips screwdriver
• chave de estrela = cross-head / star-type screwdriver, depending context

So chave de fendas is correct, but it is more specific than the English word screwdriver can sometimes be.

Because in Portuguese, adjectives often come after the noun, especially when they are descriptive or classifying.

So:

• fita adesiva = adhesive tape

is the normal order.

Putting adesiva before fita would sound unnatural here. In this case, the noun + adjective order is the standard pattern.

Yes, you can change the order:

• Enquanto o pintor trabalhava, eu segurava a fita adesiva e a chave de fendas.
• Eu segurava a fita adesiva e a chave de fendas enquanto o pintor trabalhava.

Both are correct.

As for the comma: when the enquanto clause comes first, Portuguese normally separates it from the main clause with a comma. When the enquanto clause comes second, the comma is often omitted unless the writer wants an extra pause or emphasis.