Kız kardeşimin burnu tıkalı, yine de okula gitti.

Because kız kardeşimin means of my sister / my sister's.

Breakdown:

• kız kardeş = sister
• kız kardeşim = my sister
• kız kardeşimin = my sister's

The ending -in / -ın / -un / -ün is the genitive ending, which marks the possessor. In this sentence, my sister is the possessor of the nose, so Turkish marks that relationship directly.

Because burnu is the possessed form: her/his/its nose.

In Turkish possession, you usually mark both parts:

• possessor: kız kardeşimin = my sister's
• possessed thing: burnu = her nose

So the pattern is:

kız kardeşimin burnu = my sister's nose

Also, burun changes to burnu when the possessive ending is added. This is a common sound change in Turkish called vowel drop:

• burun
• burun + -u
• burnu

Because Turkish usually expresses possession with suffixes, not with separate words like her.

English says:

• my sister's nose
• or her nose

Turkish says both parts through endings:

• kız kardeşimin = my sister's
• burnu = her nose / the nose belonging to her

So her is already built into the grammar of the phrase. You do not need an extra pronoun.

Yes. Kız kardeş literally means girl sibling, and in normal English that is simply sister.

Turkish often uses:

• kız kardeş = sister
• erkek kardeş = brother
• kardeş = sibling / brother / sister, depending on context

So here kız kardeşimin is simply my sister's.

Tıkalı means blocked, clogged, stopped up.

With burun it commonly means:

• stuffy
• blocked up
• congested

So burnu tıkalı literally means her nose is blocked, but naturally in English you might say she has a stuffy nose.

Because in Turkish, the verb to be is often not expressed in the 3rd person present tense.

So:

• burnu tıkalı = her nose is blocked

There is no separate word like English is.

This is very normal in Turkish:

• Hava güzel. = The weather is nice.
• Ev büyük. = The house is big.
• Burnu tıkalı. = Her nose is blocked.

If you wanted the past, Turkish would show it:

• burnu tıkalıydı = her nose was blocked

This is normal in Turkish. The first clause describes a state, and the second clause tells the main completed action.

• burnu tıkalı = her nose is blocked / she has a stuffy nose
• okula gitti = she went to school

In context, Turkish can use the present-form predicate to describe the condition surrounding the event. It can sound like:

• My sister had a stuffy nose, but she still went to school.

If you want to make the first clause explicitly past too, you can say:

• Kız kardeşimin burnu tıkalıydı, yine de okula gitti.

That version is also very natural.

Yine de means even so, nevertheless, still, or despite that.

It shows contrast: the first clause gives a reason something might not happen, but the second clause says it happened anyway.

So here:

• her nose was blocked
• yine de = even so
• she went to school

It is stronger and more specific than just ama (but) because it emphasizes despite the situation.

Because gitmek usually takes the dative case when you say where someone goes.

• okul = school
• okula = to school

So:

• okula gitti = she went to school

Compare:

• okulda = at school / in school
• okulu = the school (object form, accusative)

Since the action is movement toward school, Turkish uses -a / -e here.

Gitti comes from gitmek = to go.

Breakdown:

• git- = verb stem
• -ti = past tense ending

So:

• gitti = he/she/it went

Turkish often leaves the subject unstated if it is clear from context. In this sentence, the understood subject is my sister.

Yes. The subject is understood from the previous clause.

The sentence says:

• Kız kardeşimin burnu tıkalı = my sister's nose is blocked
• yine de okula gitti = even so, she went to school

Turkish does not need to repeat o or kız kardeşim if the subject is already obvious.

The sentence is natural as written, but Turkish word order is somewhat flexible.

This version is standard:

• Kız kardeşimin burnu tıkalı, yine de okula gitti.

You could also hear:

• Kız kardeşimin burnu tıkalıydı, yine de okula gitti.
• Yine de okula gitti.
• Okula yine de gitti.

Changing the order usually changes emphasis, not the core meaning. Turkish often places the most important or focused information near the verb or earlier for contrast.