El inquilino dejó el piso limpio, así que la dueña le devolvió la fianza.

Both word orders are possible, but dejó el piso limpio is the most neutral and natural here.

The pattern is:

dejar + direct object + adjective

So:

• dejó el piso limpio = he left the flat clean

This adjective, limpio, describes the state of the flat after the action. It works a bit like English left the flat clean.

You can also say dejó limpio el piso, but that word order often feels a bit more stylistic or emphatic.

Because limpio is an adjective meaning clean, while limpiado is a past participle meaning cleaned.

In this sentence, Spanish is describing the condition of the flat, not the action in a passive-like way.

• dejó el piso limpio = he left the flat clean
• limpiado would suggest something more like cleaned, which does not sound natural here

Spanish often uses an adjective after dejar to describe the result:

• dejar la puerta abierta = to leave the door open
• dejar la mesa ordenada = to leave the table tidy
• dejar el piso limpio = to leave the flat clean

In Spain, piso commonly means flat or apartment.

So in this sentence:

• el piso = the flat / the apartment

This is very common in Peninsular Spanish. A learner may already know apartamento, but in Spain:

• piso is the everyday word for a flat/apartment
• apartamento is often used for holiday apartments, tourist accommodation, or sometimes smaller apartments

So here piso is the most natural choice.

They refer to opposite sides of the rental arrangement:

• el inquilino = the tenant
• la dueña = the female owner / landlady

A few useful related words:

• el dueño = the male owner / landlord
• la propietaria = the female property owner, a bit more formal
• el arrendatario / la arrendataria = very formal, legal word for tenant

In everyday Spanish, inquilino and dueña are very natural.

Spanish usually uses the definite article with nouns in cases where English often does not.

So:

• la dueña = the owner / the landlady

Even if English might say the landlady or sometimes just landlady in a different context, Spanish generally wants the article here.

The sentence is talking about a specific owner and a specific tenant, so el inquilino and la dueña are both perfectly normal.

Because la fianza is the thing being returned, so it is the direct object, and le refers to the person who receives it.

Breakdown:

• la fianza = the deposit → direct object
• le = to him / to her → indirect object

So:

• la dueña le devolvió la fianza = the owner returned the deposit to him

You could expand it as:

• la dueña le devolvió la fianza al inquilino

That makes the roles very clear.

If you used la instead of le, it would refer to a feminine direct object, which would not fit here.

In this context, la fianza means the deposit, especially a rental deposit.

In Spain, this is the money a tenant gives at the start of a tenancy as a guarantee against damage, unpaid rent, and so on.

So:

• devolver la fianza = to give back the deposit
• perder la fianza = to lose the deposit
• pagar una fianza = to pay a deposit

This is a very common housing word in Spain.

Because it describes a completed action in the past.

• dejó = left
• devolvió = returned / gave back

The sentence presents two finished events:

1. the tenant left the flat clean
2. the owner returned the deposit

That is exactly the kind of situation where Spanish normally uses the pretérito indefinido.

If you used the imperfect, it would sound like background information or a repeated/habitual action, which does not fit this one-time event.

Así que means so, therefore, or as a result.

It connects the two parts of the sentence:

• El inquilino dejó el piso limpio
• así que
• la dueña le devolvió la fianza

So the idea is:

The tenant left the flat clean, so the landlady returned his deposit.

It shows consequence: one thing led to the other.

Yes, but the nuance changes a little.

• así que = so / therefore, very natural for consequence
• por eso = for that reason / that’s why
• entonces = then / so, depending on context

Possible alternatives:

• El inquilino dejó el piso limpio, por eso la dueña le devolvió la fianza.
• El inquilino dejó el piso limpio, entonces la dueña le devolvió la fianza.

All are understandable, but así que is especially natural when one event directly leads to the next.

In Spain, devolver is the normal and best verb here.

• devolver = to return, to give back

So:

• le devolvió la fianza = she returned the deposit to him

Regresar in Spain usually means to return oneself somewhere, like to come back, rather than to give something back. In some varieties of Latin American Spanish, regresar algo can be heard, but for Spain, devolver is the safest and most natural choice.

Because le already means to him or to her.

Spanish often uses just the indirect object pronoun when the meaning is clear from context:

• la dueña le devolvió la fianza = the owner returned the deposit to him

You can add a él or al inquilino for emphasis or clarity:

• la dueña le devolvió la fianza al inquilino
• la dueña le devolvió la fianza a él

But it is not necessary here, because el inquilino has already been mentioned.

Literally, dueña means female owner.

In this context, because we are talking about a rental property, it can naturally be translated as landlady. But the core meaning is simply owner.

So depending on the translation style, both work:

• the owner returned the deposit
• the landlady returned the deposit

If you want a more specifically property-related word, propietaria is also possible, though a bit more formal.

You would change el inquilino to la inquilina:

• La inquilina dejó el piso limpio, así que la dueña le devolvió la fianza.

Notice that le stays the same, because le can mean to him or to her.

If the owner were male, you would say:

• El inquilino dejó el piso limpio, así que el dueño le devolvió la fianza.

So the article and noun change according to gender, but the basic structure stays the same.