Pagué veinte dólares.

It comes from the infinitive pagar, meaning to pay.

Pagué is:

• first person singular: I
• preterite tense: a completed past action

So pagué means I paid.

The accent mark shows that the stress falls on the last syllable: pa-GUÉ.

It also helps distinguish this form from pague, which can be:

• the present subjunctive form
• the formal command form

So the accent is important both for pronunciation and grammar.

A rough English-friendly guide is pah-GEH.

A few useful points:

• The g is a hard g sound, like in get
• The u in gue is silent
• The stress is on the last syllable because of the accent: pa-GUÉ

So it is not pronounced like pa-goo-AY.

In Spanish spelling, gue and gui usually have a silent u.

This is done to keep the g hard before e or i.

Compare:

• gato → hard g
• guerra → hard g, with silent u
• pagué → hard g, with silent u

If Spanish wants the u to be pronounced in gue/gui, it uses a diaeresis:

• vergüenza
• pingüino

It uses the preterite: pagué.

You use the preterite for a completed action in the past:

• Pagué veinte dólares ayer.
• Pagué en efectivo.

In Spain, learners should also know that speakers often use the present perfect for recent past actions connected to today or the present:

• He pagado veinte dólares.

Very roughly:

• Pagué = a finished past event
• He pagado = I have paid / I paid, often with a present connection

Both are correct Spanish, but in Spain this distinction is especially useful.

Spanish often leaves out subject pronouns because the verb ending already shows who the subject is.

Pagué already tells us the subject is I.

So:

• Pagué veinte dólares. = normal
• Yo pagué veinte dólares. = also correct, but more emphatic

You might include yo if you want contrast:

• Yo pagué veinte dólares, no él.

Because Spanish numbers normally do not change for singular or plural in this way.

So:

• veinte dólares
• treinta dólares
• cien dólares

The noun changes if needed:

• un dólar
• dos dólares

So veinte stays veinte, while dólar becomes dólares.

The singular is dólar, and the plural is dólares.

Both have written accents because the stress falls earlier than the default pattern would suggest:

• DÓ-lar
• DÓ-la-res

In dólares, the stress is on the first syllable. Spanish marks this with an accent because it is a word stressed before the second-to-last syllable.

Because with pagar, the amount paid can be the direct object.

So:

• Pagué veinte dólares. = I paid twenty dollars.

If you want to say what you paid the money for, you often use por:

• Pagué veinte dólares por el libro.

If you want to say who received the payment, you can use a:

• Le pagué veinte dólares al taxista.

So in your sentence, veinte dólares is simply the amount paid.

Yes, it is completely grammatical and natural.

The only cultural note is that in Spain, people usually talk about euros, not dólares, in everyday situations. So in many real-life Spain contexts, you would more often hear:

• Pagué veinte euros.

But if the payment really was in dollars, Pagué veinte dólares is perfectly fine.

Yes, but Pagué veinte dólares is the most neutral and standard order.

Other orders are possible for emphasis, for example:

• Yo pagué veinte dólares.
• Veinte dólares pagué.

But those sound more marked or contrastive. For normal use, stick with:

• Pagué veinte dólares.

Yes. The basic meaning is I paid twenty dollars, but depending on context and emphasis, it can also correspond to I did pay twenty dollars.

For example:

• Sí, pagué veinte dólares.

Spanish often uses intonation or context for that kind of emphasis, rather than a special extra word like English did.

Usually not in a basic sentence like this.

• Pagué veinte dólares. = I paid twenty dollars.

You would use an article only if you mean a specific twenty dollars already known in the conversation:

• Pagué los veinte dólares que te debía.

So without extra context, veinte dólares is the normal choice.