Yılbaşı planı netleşince, annem misafirler için börek yapacak.

Yılbaşı literally means the beginning/head of the year, and in everyday Turkish it usually refers to New Year or New Year’s Eve / the New Year period, depending on context.

So in this sentence, yılbaşı planı means the New Year plan or the plan for New Year.

Because yılbaşı planı is a Turkish noun compound.

In Turkish, when one noun modifies another, the second noun often takes the 3rd person possessive suffix. So:

• yılbaşı = New Year
• planı = its plan / the plan of it

Together, yılbaşı planı means New Year plan or the plan for New Year.

This is a very common structure in Turkish:

• okul kapısı = school door
• şehir merkezi = city center
• yaz tatili = summer vacation

So planı does not mean someone specifically owns the plan; it is just the normal compound form.

Netleşince means when it becomes clear, once it is finalized, or after it gets settled.

It comes from:

• net = clear
• netleşmek = to become clear / to get finalized
• netleşince = when it becomes clear

So Yılbaşı planı netleşince means when the New Year plan becomes clear or once the New Year plan is finalized.

It is made from the verb netleşmek plus the suffix -ince / -ınca, which often means when, once, or after.

Breakdown:

• netleş- = become clear
• -ince = when/once

So:

• gelince = when he/she comes
• bitince = when it finishes
• netleşince = when it becomes clear

This suffix creates a subordinate time clause.

Because Turkish very often puts time clauses before the main clause.

So the sentence structure is:

• Yılbaşı planı netleşince = when the New Year plan is finalized
• annem misafirler için börek yapacak = my mother will make börek for the guests

This order is very natural in Turkish. English can do the same:

• When the New Year plan is finalized, my mother will make börek for the guests.

Turkish can sometimes change the order for emphasis, but this sentence is in a very standard, natural arrangement.

Because anne means mother, and the suffix -m means my.

So:

• anne = mother
• annem = my mother

This is a possessive ending, not a separate word like English my.

Other examples:

• babam = my father
• ablam = my older sister
• arkadaşım = my friend

Misafirler için means for the guests.

Breakdown:

• misafir = guest
• misafirler = guests
• için = for

So misafirler için tells us who the börek is intended for.

You can use için with many nouns and pronouns:

• senin için = for you
• çocuklar için = for the children
• akşam için = for the evening

Because the sentence is talking about guests in general, more than one guest.

• misafir = guest
• misafirler = guests

The plural suffix is -ler / -lar, depending on vowel harmony.

Here it is -ler because of the vowels in misafir.

Börek is a very common Turkish savory pastry, usually made with thin dough and filled with things like:

• cheese
• spinach
• minced meat
• potatoes

So in this sentence, it is not just any food item; it is a culturally familiar dish often made for guests.

Yapacak is the future tense form of yapmak (to do / to make).

Breakdown:

• yap- = make/do
• -acak = future tense

So yapacak means he/she will make or he/she will do.

Because the subject is already given as annem, yapacak here means:

• my mother will make

Because Turkish often leaves out subject pronouns when they are already clear from context.

In this sentence, the subject is explicitly stated as annem, so there is no need to add o (she).

Turkish commonly does this:

• Annem gelecek. = My mother will come.
• Babam aradı. = My father called.
• Öğretmen konuşuyor. = The teacher is speaking.

A separate pronoun would usually be added only for emphasis or contrast.

Yes. That is a very natural translation.

The suffix -ince can often be translated in several ways depending on context:

• when
• once
• after

So here all of these can work:

• When the New Year plan is finalized...
• Once the New Year plan is finalized...
• After the New Year plan is finalized...

The exact English choice depends on style more than grammar.

It is neither passive in the English sense nor something you should think of as fully active like to finalize something.

Netleşmek is an intransitive verb meaning to become clear or to get settled/finalized. The thing itself becomes clear.

Compare:

• Planı netleştireceğiz. = We will finalize the plan.
  (netleştirmek = to make something clear/finalize something)

• Plan netleşecek. = The plan will become clear / be finalized.
  (netleşmek = to become clear)

So in your sentence, the plan is the thing that becomes settled.

Yes, Turkish word order is flexible, but not every version sounds equally neutral.

The given sentence:

• Yılbaşı planı netleşince, annem misafirler için börek yapacak.

is the most neutral and natural version.

You could also say:

• Annem, yılbaşı planı netleşince misafirler için börek yapacak.

This is also correct, but it puts annem slightly more into focus.

Turkish often moves words around for emphasis, but the original version is probably the best one for a learner to treat as the default.

The comma separates the subordinate time clause from the main clause:

• Yılbaşı planı netleşince, = when the New Year plan is finalized
• annem misafirler için börek yapacak. = my mother will make börek for the guests

In writing, this helps readability. In speech, there is usually a small pause there too.

Not without changing the meaning or making the sentence less clear.

• misafirler için börek yapacak = she will make börek for the guests
• misafirlere börek yapacak would sound odd, because börek yapmak normally means to make börek, not to make börek to someone

So için is the natural choice when you want to say the börek is intended for the guests.

Turkish does not mark definiteness in exactly the same way English does.

For example:

• Yılbaşı planı can mean the New Year plan or a New Year plan, depending on context.
• misafirler can mean the guests or just guests, again depending on context.

In this sentence, English would most naturally say:

• When the New Year plan is finalized, my mother will make börek for the guests.

But the Turkish itself does not force exactly the same definite/indefinite distinctions that English does.