Nisan sonunda muhtar hanım, mahalledeki ilkbahar şenliğini duyurdu.

Turkish often uses a compound-like pattern X sonu for the end of X.

• Nisan sonu = the end of April
• Nisan sonunda = at/in the end of April

So sonunda is built from sonu + locative -da. The -n- is a buffer consonant that appears before the case ending. You may also hear Nisan'ın sonunda, which is a more explicitly possessive version, but Nisan sonunda is very common.

A muhtar is an elected local head of a village or urban neighborhood in Turkey. In this sentence, because mahalle means neighborhood, muhtar refers to the neighborhood head.

There is no perfect one-word English equivalent, so translations vary: neighborhood head, local head, or sometimes just muhtar.

Hanım is a polite title for a woman, roughly like Ms., Mrs., or Madam, depending on context.

So muhtar hanım is a respectful way to refer to a female muhtar. It sounds more polite than just saying muhtar by itself.

Mahalledeki means the one in the neighborhood or located in the neighborhood.

It breaks down like this:

• mahalle = neighborhood
• -de = in / at
• -ki = turns that location phrase into something that can modify a noun

So:

• mahallede = in the neighborhood
• mahalledeki şenlik = the festival in the neighborhood

It describes which festival it was.

So mahalledeki ilkbahar şenliğini means the spring festival in the neighborhood.

It does not primarily mean that the act of announcing happened in the neighborhood. If you wanted to emphasize the location of the announcement itself, you would more naturally use mahallede without -ki.

Because ilkbahar şenliği is not just a plain adjective + noun combination. It is a very common Turkish noun-compound pattern.

• ilkbahar = spring
• şenlik = festival
• ilkbahar şenliğ-i = spring festival

In Turkish, in this kind of compound, the second noun usually takes this ending. So the -i here is already part of the phrase spring festival.

Because the whole phrase is the specific direct object of the verb duyurdu.

Turkish often marks a specific/definite direct object with the accusative. So:

• ilkbahar şenliği = spring festival
• ilkbahar şenliğini = the spring festival (as a specific object)

More technically, this is:

• şenliğ-i = festival in the compound
• -ni = accusative added after that

So the sentence is talking about a particular, identifiable spring festival.

This is a common sound change in Turkish called consonant softening.

A final k often changes to ğ when a vowel-initial ending is added:

• şenlik
• şenliğ-i
• şenliğ-i-ni

So the spelling changes, but it is a regular pattern.

Duyurdu is:

• simple past tense
• third person singular

So it means he/she announced.

Here the subject is already stated as muhtar hanım, so Turkish does not need a separate word for she.

Yes.

• duymak = to hear
• duyurmak = to make heard, to announce

So duyurmak is related to duymak, but in actual use it is best learned as the normal verb meaning to announce.

Because Turkish commonly uses Subject–Object–Verb order, and the verb very often comes last.

This sentence is arranged like this:

• Nisan sonunda = time expression
• muhtar hanım = subject
• mahalledeki ilkbahar şenliğini = object
• duyurdu = verb

That order is very natural in Turkish.

Yes. Turkish word order is flexible, and changing it often changes emphasis more than basic meaning.

For example:

• Muhtar hanım Nisan sonunda mahalledeki ilkbahar şenliğini duyurdu.
• Mahalledeki ilkbahar şenliğini muhtar hanım Nisan sonunda duyurdu.

These still mean roughly the same thing, but they highlight different parts of the sentence. The version you were given is a normal, natural order.

Not really. It is more of a stylistic pause than a strict requirement here.

Many people would also write the sentence without the comma:

Nisan sonunda muhtar hanım mahalledeki ilkbahar şenliğini duyurdu.

So the comma helps pacing or emphasis, but it is not essential to understanding the sentence.