Si mañana tienes un hueco, vamos juntas a la oficina.

In this sentence, si means if and introduces a real, possible condition:

Si mañana tienes un hueco... = If you have some free time tomorrow...

After si, Spanish normally uses the indicative, not the subjunctive, when the condition is realistic or open:

• Si vienes, salimos.
• Si tienes tiempo, vamos.

So tienes is correct.

You would use a different tense pattern for more hypothetical or unlikely situations:

• Si mañana tuvieras un hueco, iríamos...
  = If you had some free time tomorrow, we would go...

So in your sentence, si + present indicative sounds natural because the speaker sees this as a real possibility.

Here mañana means tomorrow.

It comes right after si, giving the time frame early:

Si mañana tienes un hueco...

That is very natural in Spanish. You could also move it, depending on emphasis:

• Si tienes un hueco mañana...
• Mañana, si tienes un hueco...

All of these are possible, but the original order sounds smooth and common.

A useful note: mañana can also mean morning, but in this sentence the context clearly makes it tomorrow.

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

• tienes = you have (informal singular, tú)
• vamos = we go / let’s go

So tú is not necessary unless the speaker wants emphasis, contrast, or clarity.

For example:

• Si mañana tienes un hueco... = normal
• Si mañana tú tienes un hueco... = more emphasis, maybe contrasting with someone else

English usually needs the subject pronoun, but Spanish often does not.

Because tienes is the second person singular informal form of tener.

This shows the speaker is talking to one person in an informal way, as you would with:

• a friend
• a colleague you know well
• a family member
• someone your age in a casual setting

If the speaker were addressing someone formally, it would be:

• Si mañana tiene un hueco... (usted)

If speaking to more than one person in Spain:

• Si mañana tenéis un hueco... (vosotros/vosotras)

So tienes tells you the sentence is addressed to one person informally.

Literally, hueco can mean gap, space, or hole. But in everyday Spanish, especially in contexts like scheduling, tener un hueco very often means:

• to have some free time
• to have an opening
• to have a free slot

So here it is idiomatic, not literal.

Very common examples:

• No tengo ni un hueco esta semana.
  = I don’t have a single free slot this week.
• ¿Tienes un hueco por la tarde?
  = Do you have some free time in the afternoon?

This is a very useful expression in Spain.

Yes, vamos literally is the first person plural form of ir:

• vamos = we go

But Spanish also uses this form to make suggestions, just like English let’s go:

• Vamos al cine. = Let’s go to the cinema.
• Vamos juntas a la oficina. = Let’s go together to the office.

So in this sentence, vamos is not just a plain statement about what happens. It works as a proposal or suggestion.

The whole sentence has the sense of:

If you have time tomorrow, let’s go to the office together.

Spanish often uses the present tense where English might use future wording, especially for:

1. real future situations
2. plans
3. suggestions

Here, the present appears in both parts:

• Si mañana tienes un hueco...
• vamos juntas a la oficina

This sounds natural in Spanish. It does not mean the action is happening right now.

You could use future-related forms in other versions, but the original sentence is perfectly idiomatic and conversational. Spanish often prefers simpler present forms when the time reference is already clear from words like mañana.

Juntas agrees with the people going together.

• juntas = feminine plural
• juntos = masculine plural or mixed-gender plural

So vamos juntas tells you that the speaker and the person being addressed are both female.

Examples:

• Two women: Vamos juntas
• Two men: Vamos juntos
• One man and one woman: Vamos juntos

This is an important clue in Spanish because adjectives often show gender and number agreement.

Juntas means together, but specifically with feminine plural agreement.

Grammatically, it is an adjective used in a way that describes the subject of vamos. It agrees with the implied we:

• (nosotras) vamos juntas

Spanish often uses juntos/juntas where English simply uses the adverb together.

Compare:

• Vamos juntos/juntas = We’re going together / Let’s go together
• Trabajamos juntos/juntas = We work together

So even though English uses a single invariable word, Spanish changes the form to match the people involved.

Because ir normally takes a when expressing movement toward a destination.

• ir a + place = to go to + place

So:

• Vamos a la oficina = We’re going to the office / Let’s go to the office

If you said en la oficina, that would mean in the office, describing location rather than destination.

Compare:

• Estamos en la oficina. = We are in the office.
• Vamos a la oficina. = We are going to the office.

So a is used because the sentence is about going somewhere.

The comma separates the if-clause from the main clause:

• Si mañana tienes un hueco,
• vamos juntas a la oficina.

This is common when a conditional clause comes first. It helps mark the pause and makes the structure easier to read.

In English, you would also usually write:

If you have time tomorrow, let’s go to the office together.

So the comma works similarly here.

Yes. You could say:

Si mañana tienes un hueco, vamos a la oficina.

That would still be correct. But adding juntas makes one idea more explicit: the two of you will go together.

Without juntas, the sentence could simply mean:

• we go to the office
• let’s go to the office

With juntas, the shared action is emphasized.

It also gives extra information about gender, since it shows the two people are female.

Yes, it sounds very natural in Spain Spanish, especially because of tener un hueco, which is a very common way to talk about having a free slot in your schedule.

A speaker in many Spanish-speaking places would understand it, but the expression feels especially familiar and everyday in Spain.

Also, the tone is casual and natural for spoken Spanish in Spain:

• informal tienes
• practical phrase un hueco
• simple suggestion with vamos

So for a learner focusing on Spanish from Spain, this is a very useful model sentence.