Kerah kemeja putih itu terlalu kaku, jadi saya tidak nyaman memakainya seharian.

Indonesian often links nouns directly instead of using a separate word like of.

So:

• kerah = collar
• kemeja putih itu = that white shirt / the white shirt

Together, kerah kemeja putih itu means the collar of that white shirt.

This kind of noun stacking is very common in Indonesian:

• warna mobil itu = the color of that car
• pintu rumah saya = the door of my house

The first noun is usually the main thing being talked about, and the following noun phrase tells you what it belongs to.

In this sentence, putih most naturally describes kemeja.

So:

• kemeja putih = white shirt

That means kerah kemeja putih itu is understood as the collar of that white shirt.

If you wanted to say the collar is white, you would normally phrase it differently, such as:

• kerah kemeja itu putih = the collar of the shirt is white
• kerah putih kemeja itu = the white collar of that shirt

So here, the default reading is that the shirt is white, not the collar.

Itu can mean that, but in many sentences it also helps mark something as specific/definite, similar to the in English.

So kemeja putih itu can mean:

• that white shirt
• the white shirt
  depending on context

A useful thing to notice is that itu usually comes at the end of the noun phrase:

• kemeja putih itu
• not itu kemeja putih in this kind of structure

So the whole phrase points to a particular white shirt already known in the conversation.

Because terlalu means too, while sangat means very.

• terlalu kaku = too stiff
• sangat kaku = very stiff

The sentence is expressing a problem: the collar is stiff to an uncomfortable degree. That is why terlalu is the right choice.

Compare:

• Kerahnya sangat kaku. = The collar is very stiff.
• Kerahnya terlalu kaku. = The collar is too stiff.

The second one suggests that the stiffness causes trouble.

Here, kaku means stiff in a physical sense.

It can also be used in other contexts, for example:

• physically stiff: baju ini kaku = these clothes are stiff
• socially awkward or rigid: dia kaku saat berbicara = he/she is stiff/awkward when speaking

In your sentence, because the topic is a shirt collar, the meaning is clearly physical stiffness.

Here, jadi means so or therefore.

It connects the two parts:

• Kerah kemeja putih itu terlalu kaku = The collar of that white shirt is too stiff
• jadi saya tidak nyaman... = so I am not comfortable...

This is a very common use of jadi in everyday Indonesian.

Be careful, though: jadi can also mean become in other contexts:

• Dia jadi marah. = He/She became angry.

So the meaning depends on how it is used in the sentence.

Use tidak to negate:

• verbs
• adjectives

Use bukan mainly to negate:

• nouns
• noun phrases

Since nyaman is an adjective meaning comfortable, the correct negation is:

• tidak nyaman = not comfortable

Compare:

• Saya tidak nyaman. = I am not comfortable.
• Dia bukan dokter. = He/She is not a doctor.

So bukan nyaman would sound wrong here.

Because in Indonesian, adjectives can often act directly as the predicate.

So:

• saya tidak nyaman = I am not comfortable

is completely natural.

You could also say:

• saya merasa tidak nyaman = I feel uncomfortable

Adding merasa makes the feeling a bit more explicit, but it is not necessary. Indonesian often leaves it out when the meaning is already clear.

Memakainya breaks down like this:

• meN-
  • pakai → memakai
• -nya = it / him / her / them, depending on context

So:

• memakai = to wear / to use
• memakainya = to wear it / use it

Because the object is attached at the end, Indonesian can express the whole idea in one word.

This is very common:

• membacanya = to read it
• melihatnya = to see it
• membelinya = to buy it

Most naturally, -nya refers to the shirt, not just the collar.

Even though the sentence starts by talking about the collar, the action memakai normally applies to clothing such as a shirt:

• you wear a shirt
• you do not usually say you wear a collar by itself

So the meaning is essentially:

• I am not comfortable wearing the shirt all day

The collar is the reason for the discomfort, but the thing being worn is the shirt.

If someone wanted to make this extra clear, they could say:

• jadi saya tidak nyaman memakai kemeja itu seharian

Seharian means all day or the whole day.

It is built from:

• se-
• hari = day
• -an

Together, seharian functions as an adverb of time.

Examples:

• Saya bekerja seharian. = I work all day.
• Dia tidur seharian. = He/She slept all day.

So in your sentence:

• memakainya seharian = wearing it all day

It is written as one word because it is a fixed derived form.

Because seharian tells you the duration of the action memakainya.

So:

• memakainya seharian = wear it all day

This word order is very natural in Indonesian. Time expressions often come after the verb phrase they modify.

You may also hear slight variations depending on emphasis, but the version in the sentence is the most straightforward and natural.

Yes. Both are possible, but the tone changes.

• saya = more neutral, polite, standard
• aku = more casual, personal, informal

So:

• jadi saya tidak nyaman memakainya seharian
  sounds neutral and standard

• jadi aku tidak nyaman memakainya seharian
  sounds more casual and conversational

A textbook or careful written sentence often uses saya, which is why it fits well here.