Dün acele ederken başımı kapıya çarptım.

A useful breakdown is:

• Dün = yesterday
• acele ederken = while hurrying / while in a hurry
• başımı = my head (baş
  • -ım my + -ı accusative)
• kapıya = to the door / against the door (kapı
  • -ya dative)
• çarptım = I hit / I bumped (çarp-
  • -tı past + -m I)

So the structure is roughly:

Yesterday, while hurrying, I hit my head against the door.

Acele by itself is a noun meaning haste or hurry.
To say to hurry or to be in a hurry, Turkish commonly uses the expression acele etmek.

So:

• acele = haste
• acele etmek = to hurry / to rush / to be in a hurry

This is very common in Turkish: a noun combines with etmek to make a verb.

Examples:

• yardım etmek = to help
• telefon etmek = to phone
• acele etmek = to hurry

-ken means while or when.

It connects an action to another action happening at the same time.

So:

• acele ederken = while hurrying
• yürürken = while walking
• çalışırken = while working

In this sentence, acele ederken gives the background action, and çarptım is the main event.

So the idea is:

While I was hurrying, I hit my head against the door.

Because the verb etmek behaves irregularly in this kind of form.

The stem used here is eder-, so:

• etmek
• eder
• ederken

This is something learners usually just memorize as part of the verb’s pattern.

Compare:

• gitmek → giderken
• gelmek → gelirken
• etmek → ederken

So acele ederken is the correct form.

Good question. -ken clauses do not show person directly here.

The subject is understood from the main verb:

• çarptım = I hit
• therefore acele ederken is understood as while I was hurrying

So Turkish often leaves the subject unstated when it is clear from the context or from the verb ending.

If needed, Turkish could state the subject explicitly, but it usually doesn’t:

• Ben acele ederken başımı kapıya çarptım.

That is grammatical, but ben is often unnecessary.

Because başımı contains two important endings:

• baş = head
• başım = my head
• başımı = my head as a definite direct object

The final -ı is the accusative ending, used because my head is the thing that got hit.

So:

• başım = my head
• başımı çarptım = I hit my head

This is very natural in Turkish with body parts:

• elimi kestim = I cut my hand
• ayağımı burktum = I twisted my ankle

Because çarpmak often uses the dative for the thing something hits against.

So:

• kapıya çarpmak = to hit / crash into the door
• literally, something like to strike to the door

In this sentence:

• başımı = the thing that got hit
• kapıya = the surface/object it hit against

Why not the others?

• kapıda = at/on the door → wrong meaning here
• kapıyı = the door as direct object

If you said kapıyı çarptım, that would change the structure and could suggest something more like I hit/slammed the door. But here the direct object is başımı, so kapıya is the correct form.

Çarptım breaks down like this:

• çarp- = hit / strike / bump
• -tı = past tense
• -m = I

So çarptım = I hit / I bumped

It is simple past tense, used for a completed action in the past.

This is because of consonant harmony in Turkish.

The past tense suffix has different forms:

• -dı
• -di
• -du
• -dü
• -tı
• -ti
• -tu
• -tü

After a voiceless consonant such as p, ç, t, k, the suffix usually begins with t, not d.

Since the verb stem is çarp-, and p is voiceless:

• çarp + dı → not used
• çarp + tı → çarptı
• çarptım = I hit

Because Turkish normally puts the main verb at the end.

So the pattern here is very typical:

• Dün = time
• acele ederken = background clause
• başımı kapıya = objects/complements
• çarptım = main verb at the end

That said, Turkish word order is flexible, and other orders are possible for emphasis. But the verb at the end is the most neutral and common pattern.

Yes. Turkish word order is flexible, so Dün does not have to stay at the beginning.

For example, these are possible:

• Dün acele ederken başımı kapıya çarptım.
• Acele ederken dün başımı kapıya çarptım.
• Başımı dün acele ederken kapıya çarptım.

But the first version sounds the most natural and neutral in everyday speech.

Starting with Dün is very common because Turkish often puts time expressions near the beginning of the sentence.