Nada más llegar al piso nuevo, nos pusimos a limpiar la cocina y a ordenar el salón.

Here nada más llegar means as soon as we arrived or right after arriving.

It is a very common Spanish structure for talking about something that happens immediately after another action:

• Nada más entrar, sonó el teléfono.
  As soon as we went in, the phone rang.

Even though nada más literally looks like nothing more, in this pattern it is not negative. It simply means immediately after.

Because after nada más, Spanish often uses an infinitive to express upon doing something / as soon as doing something.

So:

• Nada más llegar... = As soon as we arrived...

The subject of llegar is understood from the main clause. In this sentence, it is the same people as nos pusimos: we.

Because the verb llegar normally uses a before the destination:

• llegar a casa
• llegar al trabajo
• llegar al piso

Here, a + el contracts to al:

• a el piso nuevo → al piso nuevo

So llegar al piso nuevo is the normal way to say arrive at the new flat.

Because llegar expresses movement toward a destination, so Spanish uses a, not en:

• llegar a un lugar = arrive at a place

En would describe being somewhere, not arriving there.

Compare:

• Llegamos al piso nuevo. = We arrived at the new flat.
• Estábamos en el piso nuevo. = We were in the new flat.

In Spain, piso very commonly means flat/apartment.

So el piso nuevo here most naturally means the new flat or the new apartment.

This is a good Spain-specific word to know. In other varieties of Spanish, learners may hear apartamento more often.

Also, piso can literally mean floor in other contexts, so the meaning depends on context.

Not always.

Nuevo can mean:

• newly built / brand-new
• new to the speakers (for example, a flat they have just moved into)

In this sentence, the most natural reading is often the flat they had just moved into, not necessarily a newly built one.

This comes from the expression ponerse a + infinitive, which means:

• to start doing something
• to get down to doing something

So:

• nos pusimos a limpiar = we started cleaning

It is best learned as a fixed expression rather than trying to translate poner literally as to put here.

Because the verb here is ponerse, not plain poner.

The reflexive pronoun is part of the expression:

• me pongo a estudiar
• te pones a leer
• se pone a cocinar
• nos ponemos a limpiar

In the preterite:

• nos pusimos a limpiar

Without nos, the meaning would be different, because poner and ponerse are not the same verb.

Because ponerse a requires a before the infinitive:

• ponerse a limpiar
• ponerse a ordenar

When two infinitives are joined, Spanish often repeats the preposition:

• nos pusimos a limpiar la cocina y a ordenar el salón

That repetition sounds natural and clear. You may also hear the second a omitted in some cases, but repeating it is very common and completely normal.

Because Spanish often uses the definite article in places where English would also use the, and sometimes even where English might choose a different structure.

Here it is simply the normal way to refer to those rooms:

• limpiar la cocina
• ordenar el salón

That is just standard Spanish usage for clean the kitchen and tidy the living room.

In Spain, salón usually means the living room or the main sitting area of the home, sometimes including the dining area too.

So ordenar el salón means to tidy the living room.

This is another useful Spain-specific word. In some contexts, learners may also know sala, but salón is very common in everyday Peninsular Spanish for the main room of the house.

Because the sentence tells a sequence of completed actions in the past:

1. they arrived
2. they started cleaning and tidying

The preterite nos pusimos presents that as a finished event in the story.

If you used the imperfect, it would sound more like background, habit, or an ongoing situation, which is not the main idea here.

The subject is the same as the subject of the main clause: we.

Spanish often leaves subjects unstated when they are already clear, so:

• Nada más llegar...
• nos pusimos...

Both actions are understood to refer to we/us.

Yes. A few natural alternatives are:

• Al llegar al piso nuevo, nos pusimos a limpiar la cocina y a ordenar el salón.
• En cuanto llegamos al piso nuevo, nos pusimos a limpiar la cocina y a ordenar el salón.
• Nada más llegar al piso nuevo, empezamos a limpiar la cocina y a ordenar el salón.

They are all similar, but nada más llegar gives a particularly strong sense of immediately after arriving.