İlk yardım eğitmeni ilk yardımcıyı değerlendirdi.

Because ilk yardım eğitmeni is a noun compound, not just an adjective + noun combination.

• ilk yardım = first aid
• eğitmen = trainer / instructor
• ilk yardım eğitmeni = first aid trainer

In Turkish, in this kind of compound, the second noun often takes a 3rd person possessive-looking ending:

• matematik öğretmeni = math teacher
• spor salonu = gym
• ilk yardım eğitmeni = first aid trainer

So here, -i is part of the compound structure. It does not mean the word is the object.

The subject is still ilk yardım eğitmeni.

That -yı is the accusative ending, which marks a specific direct object.

• yardımcı = helper / assistant
• ilk yardımcı = first aider
• ilk yardımcıyı = the first aider as the object of the verb

So the sentence shows that the first aider is the one being evaluated.

Why -yı and not just -ı?

Because yardımcı ends in a vowel, Turkish adds a buffer consonant y before the accusative suffix:

• yardımcı + ı → yardımcıyı

This is very common:

• arabayı
• kapıyı
• öğrenciyi

Turkish shows this mainly through case marking, not just word order.

• ilk yardım eğitmeni has no accusative marker, so it is the subject
• ilk yardımcıyı has the accusative marker -yı, so it is the direct object
• değerlendirdi = evaluated

So:

• the first aid trainer = the one who did the action
• the first aider = the one affected by the action

This is one reason Turkish can sometimes change word order more freely than English.

They are related, but they mean different things.

• ilk yardım = first aid
  This is the act, field, or procedure.

• ilk yardımcı = first aider
  This is the person who gives first aid.

So:

• ilk yardım eğitmeni = first aid trainer
• ilk yardımcı = first aider

A useful way to remember it:

• yardım = help / aid
• yardımcı = helper / assistant

Yes. It follows the common Turkish pattern:

Subject + Object + Verb

So here:

• İlk yardım eğitmeni = subject
• ilk yardımcıyı = object
• değerlendirdi = verb

That is a very standard Turkish sentence structure.

Could the order change? Yes, sometimes, especially for emphasis. But the neutral order is exactly what you see here.

Turkish does not use articles the way English does.

There is no direct equivalent of the in most sentences, and a/an is often expressed by bir when needed.

In this sentence, definiteness is understood from structure and context:

• the object ilk yardımcıyı is clearly specific because it has the accusative ending
• the subject is interpreted from context

So English may need the or a, but Turkish often does not say them explicitly.

değerlendirdi comes from the verb değerlendirmek, meaning to evaluate / assess.

Breakdown:

• değerlendir- = verb stem, evaluate
• -di = past tense

So değerlendirdi means he/she evaluated or evaluated.

Turkish often leaves the subject pronoun unstated, so the verb by itself can mean:

• he evaluated
• she evaluated
• or simply evaluated, depending on context

In this sentence, the subject is already stated as ilk yardım eğitmeni.

Not here.

By itself, eğitmeni could sometimes mean his/her trainer in another sentence, depending on context. But in ilk yardım eğitmeni, it is best understood as part of a fixed noun-compound pattern:

• ilk yardım eğitmeni = first aid trainer

So the -i here is not telling you his/her. It is mainly the normal form of the second noun in this kind of compound.

This is a very common point of confusion for English speakers, because the ending looks possessive even when the whole phrase is just naming a type of person or thing.

Because the two phrases are built differently.

1. ilk yardım eğitmeni

This is a noun + noun compound:

• ilk yardım = noun phrase
• eğitmen = noun
• together: first aid trainer

In this structure, the second noun takes that compound ending: eğitmeni.

2. ilk yardımcı

This is more like adjective + noun:

• ilk = first
• yardımcı = helper / assistant
• together: first aider

So yardımcı does not take the same compound ending here.

This sentence is useful because it contains both sounds.

i

This is the dotted i, pronounced roughly like ee in see, but usually shorter.

Examples:

• ilk
• eğitmeni
• değerlendirdi

ı

This is the dotless ı, a sound English does not really have.
It is a relaxed, central vowel, somewhat like the vowel in the second syllable of sofa, but not exactly.

Examples:

• yardım
• yardımcıyı

A very rough pronunciation guide:

• ilk ≈ ilk
• yardım ≈ yar-duhm
• yardımcıyı ≈ yar-duhm-juh-yuh
• değerlendirdi ≈ deh-er-len-dir-di

Not perfect English spellings, but enough to help you hear the difference.

In Turkish, a specific direct object usually takes the accusative ending.

So:

• ilk yardımcıyı değerlendirdi = evaluated the first aider / evaluated a particular first aider

If you removed the accusative, you would get:

• ilk yardımcı değerlendirdi

But that would be confusing here, because ilk yardımcı could then look like a subject rather than an object.

More generally, the accusative helps Turkish show that the noun is:

• the direct object
• and usually specific/known in context

So -yı is doing important grammatical work in this sentence.