He revisado el índice, pero todavía quiero añadir otro apartado sobre el viaje.

He revisado is the pretérito perfecto in Spanish. In Spain, this tense is very commonly used for actions connected to the present, especially when the speaker sees the action as relevant now.

So He revisado el índice suggests:

• I have reviewed the index
• and that review matters for what follows: but I still want to add another section...

In many parts of Latin America, revisé might be more common in the same situation. In Spain, he revisado sounds very natural here.

Here, he is not the pronoun he from English.

It is the first-person singular present form of the auxiliary verb haber:

• yo he
• tú has
• él/ella ha
• nosotros hemos
• vosotros habéis
• ellos han

So:

• he revisado = I have reviewed

The full subject yo is omitted because Spanish often leaves out subject pronouns when the verb already makes the person clear.

Spanish often drops subject pronouns because the verb ending usually tells you who the subject is.

• quiero already means I want
• he revisado already means I have reviewed

So Yo he revisado el índice... is possible, but it is usually unnecessary unless you want emphasis, contrast, or clarity.

Here índice most likely means index or table of contents, depending on the context.

Common possibilities:

• in a book: index
• in a report or document: contents / outline / table of contents
• in other contexts, it can also mean indicator or rate

Because the sentence talks about adding otro apartado, it sounds like a structured text or document, so table of contents or outline may fit well.

Spanish often uses the definite article where English might sometimes omit it.

Here el índice means the index / the table of contents, referring to a specific one already understood from context.

Using el sounds natural because the speaker is talking about a particular document’s index, not the concept of an index in general.

Pero means but and introduces a contrast.

The contrast is:

• I have reviewed the index
• but I still want to add another section

So the idea is: even though the review is done, the speaker is not finished making changes.

Yes, todavía and aún can both mean still here.

• todavía quiero añadir...
• aún quiero añadir...

Both are natural. In everyday speech, todavía is very common and clear.

In this sentence, todavía shows that the desire to add something continues even after reviewing the index.

Placing todavía before quiero is the most natural position here because it modifies the whole idea of still wanting.

• todavía quiero añadir... = I still want to add...

You may also hear different placements in Spanish depending on emphasis, but this one is the standard and most neutral choice.

After a verb like querer, Spanish normally uses an infinitive for the next verb:

• quiero añadir = I want to add
• quiero comer = I want to eat
• quiero salir = I want to leave

So you do not say:

• quiero añado ❌

This is the same basic pattern as in English: want + infinitive.

Yes, agregar is possible, but añadir sounds very natural in Spain, especially in writing or formal contexts.

• añadir otro apartado = very natural in Spain
• agregar otro apartado = understandable, but may sound less typically European Spanish in some contexts

Other possible verbs depending on nuance:

• incluir = to include
• incorporar = to incorporate
• meter = informal, less suitable here

So añadir is a very good choice for this sentence.

In this context, apartado means something like:

• section
• subsection
• heading
• part

It is commonly used for parts of a text, form, document, or report.

So otro apartado means another section or another item/part in the structure of the document.

In Spanish, otro usually does not take un before it.

So:

• otro apartado = another section ✅
• un otro apartado ❌

This is similar to:

• otra idea = another idea
• otro día = another day

Only in very special or unusual structures would you see something different, but for normal usage, otro goes by itself.

Sobre here means about or on the topic of.

So:

• un apartado sobre el viaje = a section about the trip/journey

This is a very common way to introduce the topic of a section:

• un libro sobre historia
• un artículo sobre arte
• una charla sobre tecnología

You could sometimes say acerca del viaje, but sobre el viaje is simpler and very natural.

Usually no, not with the same meaning.

• sobre el viaje = about the trip ✅
• del viaje = of the trip / from the trip — different meaning

If you say un apartado del viaje, it sounds more like a section that belongs to the trip in some way, which is not the intended idea. The sentence wants to express the topic of the new section, so sobre is the right preposition.

Yes, two useful points:

• índice has a written accent on the first syllable: ÍN-di-ce
• añadir contains ñ, which is pronounced like the ny sound in canyon: a-nya-DIR

Also:

• apartado is stressed on -ta-: a-par-TA-do
• todavía has the stress on -ví-: to-da-VÍ-a

These accents help show where the stress goes, which is very useful for correct pronunciation.