Μην τσαλακώνεις το έγγραφο, πρέπει να το βάλω στο ντοσιέ.

Because μην is the word Greek uses to make a negative command or to negate a subjunctive verb.

• Μην τσαλακώνεις ... = Don’t crumple ...
• You do not use δεν here. Δεν negates statements, not commands.

So:

• Δεν τσαλακώνεις το έγγραφο would mean something like You are not crumpling the document
• Μην τσαλακώνεις το έγγραφο means Don’t crumple the document

For learners, a very useful pattern is:

μην + verb = don’t ...

Yes, by itself τσαλακώνεις is the 2nd person singular present form: you crumple / you are crumpling.

But after μην, it works as a negative command:

• Μην τσαλακώνεις = Don’t crumple / don’t be crumpling

Greek commonly uses present-looking forms like this in prohibitions.

There is also an aspect difference:

• Μην τσαλακώνεις = don’t do that action in general / don’t keep doing it / don’t start doing that
• Μην τσαλακώσεις = don’t crumple it even once / don’t end up crumpling it

So the sentence uses the imperfective form, which gives a more general don’t do that feeling.

They look the same, but they do different jobs.

1. το έγγραφο

   • Here το is the definite article
   • It means the document

2. να το βάλω

   • Here το is a clitic object pronoun
   • It means it

So:

• το έγγραφο = the document
• να το βάλω = to put it

This is very common in Greek because the article and the neuter singular object pronoun are both το.

It is in the accusative singular, because it is the direct object of τσαλακώνεις.

You are crumpling what?
→ the document
So το έγγραφο is the object.

A detail that can confuse learners: for many neuter singular nouns, the nominative and accusative look the same.

So:

• nominative: το έγγραφο
• accusative: το έγγραφο

Same form, different function.

Because Modern Greek normally does not use an infinitive the way English does.

English says:

• I must put it in the folder

Greek says:

• πρέπει να το βάλω

Literally, this is more like:

• it is necessary that I put it

So after πρέπει, Greek uses:

πρέπει + να + verb

This is one of the most important patterns in Greek.

This is about aspect, which is very important in Greek.

• βάλω is the perfective form
• βάζω is the imperfective form

Here, the speaker means one complete action:

• I need to put it in the folder

That is why Greek uses βάλω.

Compare:

• πρέπει να το βάλω = I need to put it in there once, as a complete action
• πρέπει να το βάζω = I need to put it in there regularly / repeatedly / as a habit

So βάλω is the natural choice here.

By itself, forms like βάλω can be tricky for English speakers, because the exact meaning depends on the structure around them.

Here, in πρέπει να το βάλω, it is a subjunctive form after να.

So the whole phrase means:

• I need to put it

Not:

• I put it
• I will put it

Compare:

• το βάζω = I put / I am putting
• θα το βάλω = I will put it
• να το βάλω = that I put it / to put it, depending on context
• πρέπει να το βάλω = I need to put it

Because weak object pronouns in Greek usually go before the verb.

So Greek says:

• να το βάλω = to put it

not:

• να βάλω το

This is standard clitic placement in Modern Greek.

A useful pattern is:

• τον βλέπω = I see him
• τη θέλω = I want her
• το βάζω = I put it
• να το βάλω = to put it
• θα το βάλω = I will put it

So the position of το here is completely normal.

Because στο is the contracted form of:

• σε + το = στο

This happens very often in Greek.

So:

• στο ντοσιέ = in / into the folder

Other common contractions are:

• σε + τον = στον
• σε + τη(ν) = στη(ν)
• σε + τα = στα

So στο is just the normal combined form.

Because Greek σε covers several meanings that English often separates:

• in
• at
• to
• sometimes into, depending on the verb and context

With a verb of movement like βάζω (put), σε often has the sense of into.

So:

• το βάζω στο ντοσιέ = I put it into the folder

Even though English prefers into, Greek naturally uses σε / στο.

Ντοσιέ means something like:

• folder
• file
• sometimes binder, depending on context

It is a borrowed word, and in Modern Greek it is usually treated as neuter:

• το ντοσιέ
• στο ντοσιέ

It is also commonly indeclinable, which means its form usually stays the same.

So learners often just memorize it as:

• το ντοσιέ = the folder/file

Because Greek often leaves subject pronouns out when they are already clear from the verb ending.

In this sentence:

• τσαλακώνεις already tells you the subject is you (singular)
• βάλω already tells you the subject is I

So Greek does not need to say εσύ or εγώ unless the speaker wants emphasis.

Compare:

• Μην τσαλακώνεις ... = Don’t crumple ...
• πρέπει να το βάλω ... = I need to put it ...

If you added the pronouns, it would sound more emphatic:

• Εσύ μην τσαλακώνεις...
• πρέπει να το βάλω εγώ

The comma separates two linked ideas:

• Μην τσαλακώνεις το έγγραφο
• πρέπει να το βάλω στο ντοσιέ

The second clause gives the reason for the first:

• Don’t crumple the document, because I need to put it in the folder

Greek often leaves out the explicit because when the connection is obvious from context.

So the comma here helps show:

request/command + explanation

Yes. That would also be very natural.

• Μην τσαλακώνεις το έγγραφο
• Μην το τσαλακώνεις

Both mean Don’t crumple the document / Don’t crumple it

The version with το έγγραφο names the object directly.
The version with το uses a pronoun instead.

Greek can also sometimes use both a noun and a pronoun together in the same sentence in certain contexts, but in this example the given wording is perfectly straightforward: first the noun is named, then in the next clause it is referred to with το.