Önlüğümü çıkarmışken, not kâğıtlarını da toplayıp çantaya koyayım.

Çıkarmışken comes from çıkarmak (to take off / remove) + -mış + -ken.

In this sentence, -mışken gives a meaning like:

• since I’ve taken off ...
• now that I’ve taken off ...
• while I’ve got ... off
• sometimes even while I’m at it

So Önlüğümü çıkarmışken means something like:

• Since I’ve taken off my apron...
• Now that I’ve taken off my apron...

It sets up the idea that the speaker has already done one thing, so they may as well do another thing too.

Because önlüğümü is the direct object of çıkarmak.

Breakdown:

• önlük = apron
• önlüğüm = my apron
• önlüğümü = my apron as a definite object

Turkish often marks definite direct objects with the accusative ending.

So:

• önlüğüm = my apron
• önlüğümü çıkardım = I took off my apron

That final -ü is the accusative ending.

These two forms are similar, but they are not the same.

• çıkarırken = while taking off / while I was taking off
• çıkarmışken = since I’ve taken off / now that I’ve taken off

So the difference is mainly this:

• çıkarırken focuses on the action in progress
• çıkarmışken suggests the action is already done, and that creates a good moment or reason to do something else

In this sentence, the speaker is not saying during the act of taking off the apron. They mean:

Now that I’ve taken it off, let me also gather the note papers and put them in the bag.

So çıkarmışken fits better.

This is a very common kind of Turkish noun structure.

The base expression is:

• not kâğıdı = note paper / sheet of note paper

This is a noun compound. In Turkish noun compounds, the second noun often takes a possessive-type ending.

Then we make it plural and definite object:

• not kâğıtları = note papers / sheets of note paper
• not kâğıtlarını = the note papers, as a definite object

A useful breakdown is:

• kâğıt = paper
• kâğıtlar = papers
• kâğıtları = note papers
• kâğıtlarını = the note papers (object form)

So not kâğıtlarını toplamak means to gather the note papers.

Here da means too / also / as well.

So:

• not kâğıtlarını toplayıp çantaya koyayım = Let me gather the note papers and put them in the bag.
• not kâğıtlarını da toplayıp çantaya koyayım = Let me gather the note papers too and put them in the bag.

It adds the sense that this is another thing the speaker will do, in addition to taking off the apron.

In English, depending on tone, it can feel like:

• ...let me also gather the note papers...
• ...I might as well gather the note papers too...

Toplayıp comes from toplamak (to gather / collect) + -ıp.

This -ıp / -ip / -up / -üp form is used to link actions, often like:

• and
• and then
• by doing

So:

• toplayıp çantaya koyayım = let me gather them and put them in the bag

It is a very common Turkish way to connect two verbs when the subject is the same.

For example:

• Kitapları alıp çıktım. = I took the books and left.
• Kapıyı açıp içeri girdim. = I opened the door and went in.

Here, toplayıp connects gathering and putting in the bag.

Koyayım is not simple future. It is the first-person optative / volitional form.

It usually means:

• let me put
• I’ll put
• shall I put
• I might as well put

depending on context.

So in this sentence, çantaya koyayım means:

• let me put them in the bag
• I’ll put them in the bag

It has a slightly self-suggesting tone, like the speaker is deciding on the spot:

Since I’ve taken off my apron, let me also gather the note papers and put them in the bag.

Because koymak usually takes the place you put something into in the dative case.

• çanta = bag
• çantaya = into / to the bag
• çantada = in / at the bag
• çantayı = the bag as a direct object

So:

• çantaya koymak = to put into the bag
• masaya koymak = to put on the table
• cebime koymak = to put into my pocket

Here the note papers are being moved into the bag, so çantaya is correct.

The object is understood from the earlier part of the sentence: not kâğıtlarını.

Turkish often avoids repeating the same object if it is already clear.

So the full sense is:

• not kâğıtlarını da toplayıp çantaya koyayım
• Let me gather the note papers too and put them in the bag

English can also do this:

• I’ll grab the papers and put them in the bag.

We do not need to repeat the papers after put because it is obvious.

It sounds natural and conversational. The tone is something like:

• Since I’ve taken off my apron, I might as well gather the note papers too and put them in the bag.

So the sentence expresses:

1. one action has already happened: taking off the apron
2. that creates a convenient moment
3. the speaker decides to do another task too

This is a very common Turkish way of expressing “while I’m at it” or “since I’ve already done that, let me do this too.”

The comma helps show that Önlüğümü çıkarmışken is an introductory clause.

It separates:

• the background situation: Now that I’ve taken off my apron
• from the main action: let me gather the note papers too and put them in the bag

In writing, the comma makes the sentence easier to read. In speech, there would usually be a small pause there.

It is not changing the grammar dramatically, but it clearly marks the structure of the sentence.