La conserje me abrió la puerta del edificio cuando llegué tarde a la reunión.

Not exactly.

In Spain, conserje usually means something like a building caretaker, porter, doorman, janitor, or front-desk person, depending on the context. In this sentence, it most likely means the person responsible for the building entrance, so caretaker or doorman fits well.

English concierge is usually associated more with hotels and guest services, so it is not always the best translation for conserje.

Because conserje is normally a common-gender noun. That means the noun form stays the same, and the article shows whether the person is male or female:

• el conserje = the male caretaker/doorman
• la conserje = the female caretaker/doorman

So in this sentence, la tells you the caretaker is a woman.

Me is an indirect object pronoun meaning to me or for me.

So:

• La conserje abrió la puerta = The caretaker opened the door.
• La conserje me abrió la puerta = The caretaker opened the door for me.

Spanish uses this kind of pronoun very naturally in sentences like this. In English, we often leave it implicit or use for me, but in Spanish the pronoun is very common and natural.

Because with a normal conjugated verb, object pronouns usually go before the verb in Spanish.

So you get:

• me abrió
• me dijo
• me llamó

You do not normally say abrióme in modern everyday Spanish.

Pronouns can attach to the end only with:

• infinitives: abrirme
• gerunds: abriéndome
• affirmative commands: ábreme

Because both actions are seen as completed events in the past.

• abrió = she opened
• llegué = I arrived

The sentence is talking about one specific occasion:

1. I arrived late.
2. The caretaker opened the building door for me.

That is why the preterite is the natural choice.

If you changed the tense, the meaning would change:

• cuando llegaba tarde = when I was arriving late / whenever I arrived late
• me abría la puerta = she would open the door for me / she was opening the door for me

So the preterite here gives a clear, one-time past event.

Because this sentence refers to a real event that actually happened in the past.

After cuando, Spanish uses:

• indicative for real or completed events
• subjunctive for future or not-yet-realized events

So here:

• cuando llegué tarde = when I arrived late

But for the future:

• cuando llegue tarde = when I arrive late / if I arrive late

So there is no subjunctive here because the speaker is talking about something that definitely happened.

Because de + el contracts to del in Spanish.

So:

• de + el = del
• a + el = al

That means:

• la puerta del edificio = the door of the building / the building door

This contraction is required in standard Spanish.

Because Spanish uses definite articles very often when talking about specific, identifiable things.

Here:

• la puerta = a specific door
• el edificio = a specific building
• la reunión = a specific meeting

In English, we sometimes leave things more implicit, but Spanish often prefers the article when the listener is expected to know which thing is meant.

If it were nonspecific, you might say:

• una reunión = a meeting

But here it is the meeting, not just any meeting.

Because with llegar tarde, Spanish normally uses a before the place or event you are late for.

Common patterns:

• llegar tarde al trabajo
• llegar tarde a clase
• llegar tarde a una cita
• llegar tarde a la reunión

So a la reunión is the standard choice here.

English says late to the meeting, and Spanish expresses that idea with a.

Here, tarde is an adverb, and it means late.

So:

• llegué tarde = I arrived late

This is different from la tarde, which means the afternoon.

As an adverb, tarde does not change form:

• llegué tarde
• llegaron tarde
• siempre llega tarde

You could, but it is usually less natural in this context.

The most natural Spanish way is:

• La conserje me abrió la puerta del edificio

Using para mí can sound more emphatic or contrastive, like:

• she opened it for me, not for someone else

So grammatically it is possible, but me abrió la puerta is the normal everyday phrasing.

Because of Spanish spelling rules.

The verb is llegar. In the yo form of the preterite, verbs ending in -gar change spelling to keep the hard g sound before e:

• llegar → llegué
• pagar → pagué
• jugar → jugué

If it were written llegé, the g would sound different. The u is there to preserve the pronunciation.

The accent mark on é is just the normal written accent for that preterite ending.

It can be understood either way in English, and in this context both point to the same thing: the entrance door of the building.

Spanish often uses de in places where English might use:

• of
• an apostrophe ’s
• a noun + noun structure

So:

• la puerta del edificio can mean
  • the building’s door
  • the door of the building
  • the building door

In normal context, it usually means the main door or entry door of that building.