Müdür dün istifa etti.

Because istifa etmek is a very common type of Turkish compound verb.

• istifa is a noun meaning resignation
• etmek is an auxiliary verb meaning to do / to make

Together, istifa etmek means to resign.

So:

• istifa etmek = to resign
• istifa etti = resigned

Turkish often forms verbs this way with a noun + etmek, especially with words borrowed from Arabic, Persian, or French.

Examples:

• yardım etmek = to help
• telefon etmek = to phone
• kontrol etmek = to check

Etti is the simple past, 3rd person singular form of etmek.

Breakdown:

• verb stem: et-
• past tense ending: -ti
• 3rd person singular: no extra ending here

So etti means did in form, but in this compound it gives the meaning resigned.

Why -ti and not -di? Because Turkish past-tense endings change according to sound harmony and voicing:

• after a voiceless consonant like t, the past ending appears as -tı / -ti / -tu / -tü
• here: et- → etti

Turkish has no definite article like English the.

So müdür can mean:

• the manager
• the director
• the principal

depending on context.

If you want to make it a manager, Turkish often uses bir:

• Bir müdür dün istifa etti. = A manager resigned yesterday.

Without bir, a bare noun like müdür is often understood as a specific, context-known person, so English commonly translates it as the manager.

No ending is needed because müdür is the subject of the sentence.

In Turkish, the subject is normally in the nominative, and the nominative usually has no visible ending. So the plain dictionary form is enough.

Here:

• Müdür = subject
• dün = time expression
• istifa etti = verb phrase

If müdür were used in another role, it might take a case ending:

• müdürü = the manager (as a definite direct object)
• müdüre = to the manager
• müdürde = at/on the manager
• müdürden = from the manager

But as the subject, plain müdür is correct.

Yes, this is very natural Turkish word order.

A common neutral order in Turkish is:

Subject + time + other elements + verb

So:

• Müdür dün istifa etti.

This sounds normal and straightforward.

Turkish word order is flexible, though, and moving dün changes the emphasis:

• Dün müdür istifa etti.
  Focuses more on yesterday
• Müdür istifa etti dün.
  Possible, but less neutral and more marked in everyday speech

The most important thing is that the finite verb usually comes at the end in standard Turkish main clauses.

Yes. That is also correct.

Both are grammatical:

• Müdür dün istifa etti.
• Dün müdür istifa etti.

The difference is mainly information focus:

• Müdür dün istifa etti.
  More neutral if you are talking about the manager and then saying what happened
• Dün müdür istifa etti.
  Gives more prominence to yesterday

So the choice depends on what you want to emphasize, not on right vs. wrong.

Not always. Müdür can mean several related roles depending on context:

• manager
• director
• principal (especially in a school context)
• sometimes head of a department or office

So the best English translation depends on the situation.

Also, müdür is gender-neutral. It can refer to:

• a male manager
• a female manager

Turkish nouns generally do not mark grammatical gender.

Yes, very often.

Because Turkish verbs show person, the subject can often be omitted if it is clear from context.

For example:

• Dün istifa etti. = He/She resigned yesterday.

However, in your sentence, the speaker uses müdür because they want to state explicitly who resigned.

So:

• Dün istifa etti. = okay if the person is already known
• Müdür dün istifa etti. = clearer; identifies the person as the manager

This is one of the most common features of Turkish: subjects are often omitted when they are already understood.