El archivador ocupa más espacio del que imaginaba, así que lo dejo debajo del escritorio.

In Spain, archivador is a general word for something used to store documents. Depending on the context, it can mean a filing cabinet, file box, document holder, or even a binder/lever-arch file.

In this sentence, because it takes up space and is being left under the desk, it sounds more like a fairly bulky file-storage item than a small binder.

Because ocupar espacio is the normal Spanish way to say to take up space.

• ocupar literally means to occupy
• ocupa is the third-person singular present form
• the subject is el archivador

So:

• El archivador ocupa espacio = The filing unit takes up space

This is very natural Spanish.

Because espacio is being used as an uncountable noun, just like space in English.

You say:

• más espacio = more space

not:

• más el espacio

The sentence is talking about space in a general sense, not a specific, already-defined space.

This is a very common Spanish comparison pattern.

When Spanish compares an amount or degree with what someone expected, thought, imagined, etc., it often uses:

• de lo que
• or del que / de la que / de los que / de las que

So:

• más espacio del que imaginaba = more space than I imagined

Here, del que refers back to espacio, which is masculine singular.

You may hear más espacio que imaginaba in informal speech, but del que or de lo que is the more standard pattern in this kind of sentence.

Yes, absolutely.

Both of these are possible:

• más espacio del que imaginaba
• más espacio de lo que imaginaba

The difference is small:

• del que points back more directly to espacio
• de lo que is more neutral and refers more generally to the amount

In everyday Spanish, both are common and natural.

Because imaginaba sounds natural when talking about a prior expectation or mental picture.

The imperfect often describes what you thought, expected, or had in mind, without focusing on one completed moment.

So here:

• del que imaginaba = than I had imagined / than I was imagining

Other tenses are possible, but they shift the nuance:

• imaginé focuses more on a specific moment when you imagined it
• había imaginado stresses that the imagining happened clearly before this moment

In normal speech, imaginaba is very natural in this structure.

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

It connects the first idea with the consequence:

• it takes up more space than I imagined,
• so I leave it under the desk

It is a very common way to link two clauses in Spanish.

It is similar to por eso, but not identical:

• así que works like a conjunction joining the two parts directly
• por eso means more literally for that reason / that’s why

Lo refers back to el archivador.

Because archivador is:

• masculine
• singular

the direct object pronoun is lo.

Spanish normally places object pronouns before a conjugated verb:

• lo dejo = I leave it / I put it

Compare:

• voy a dejarlo = I’m going to leave it
• déjalo = leave it

So the position of lo here is completely standard.

It can mean either, depending on the context.

Dejar often means to leave, but when talking about placing an object somewhere, it can also mean to put or to set down and leave.

In this sentence, the idea is:

• the speaker decides where to place it
• and leaves it there

So in natural English, you might translate it as either:

• so I leave it under the desk
• so I put it under the desk

Both are correct, but debajo de is especially common for literal physical location.

So:

• debajo del escritorio = under the desk
• bajo el escritorio = also under the desk

In everyday speech, debajo de often sounds a bit more natural for concrete position.

Also, del is just the contraction of:

• de + el = del

So:

• debajo de el escritorio is incorrect
• debajo del escritorio is correct

Because Spanish often drops subject pronouns when they are clear from the verb form or the context.

Here, the speaker is clearly I:

• imaginaba = I imagined / I was imagining
• dejo = I leave / I put

Spanish does not need yo unless the speaker wants emphasis, contrast, or clarity.

So:

• yo lo dejo debajo del escritorio is possible
• but lo dejo debajo del escritorio is the more neutral, natural version