Beceri rehberi olay yeri güvenliğini de içeriyor.

A natural breakdown is:

• beceri rehberi = skill guide / skills guide
• olay yeri güvenliğini = scene safety / the safety of the scene as the direct object
• de = also / too
• içeriyor = includes / is including

So the structure is:

• Subject: Beceri rehberi
• Object: olay yeri güvenliğini de
• Verb: içeriyor

This is a very normal Turkish subject–object–verb order.

Because this is an indefinite noun compound, a very common Turkish structure.

In Turkish, when one noun modifies another noun, the pattern is usually:

• first noun: bare form
• second noun: takes the 3rd person possessive suffix

So:

• beceri = skill
• rehber = guide
• beceri rehberi = skill guide

That final -i on rehberi is not the accusative here. It is part of the noun compound.

Compare:

• telefon numarası = phone number
• okul kapısı = school door
• beceri rehberi = skill guide

Olay yeri is another noun compound:

• olay = event, incident
• yer = place
• olay yeri = the place of the incident, the scene

Depending on context, it can often be translated as scene or even crime scene, though literally it is more general: incident scene.

So in this sentence, olay yeri güvenliği means scene safety or the safety/security of the scene.

Because several pieces are stacked together.

The base noun is:

• güvenlik = safety, security

Inside the compound:

• olay yeri güvenliği = scene safety

Here, güvenlik becomes güvenliği because it is the second noun in a noun compound and takes the compound ending.

Then the whole phrase is the definite direct object of içeriyor, so it also takes the accusative:

• olay yeri güvenliği
  • -(n)i → olay yeri güvenliğini

So güvenliğini contains:

• the compound form
• plus the accusative ending

That is why it looks longer.

That n is a buffer consonant.

When a word already has a possessive-type ending and then another vowel-initial suffix is added, Turkish often inserts n to make pronunciation smoother.

So:

• güvenliği
  • -i (accusative)
    becomes
• güvenliğini

This n does not add a new meaning by itself; it is just a linking sound.

Because the sentence refers to a specific thing that the guide includes: scene safety.

In Turkish, a direct object often takes the accusative when it is definite/specific.

So:

• olay yeri güvenliği = scene safety
• olay yeri güvenliğini = scene safety, specifically, as the thing being included

With verbs like içermek (to include), a definite object is very natural.

Here de means also, too, or as well.

So the sentence suggests that the skill guide includes this item in addition to something else.

For example, the sense is:

• The skill guide also includes scene safety.

It adds emphasis that this is another included element.

Because this de is the additive particle meaning also / too, and it is written as a separate word.

That is different from the suffix -de / -da meaning in / at / on, which is written attached to the word.

Compare:

• evde = in the house → suffix, attached
• ev de = the house too → particle, separate

So in your sentence:

• güvenliğini de = its/the scene safety too

Both can be possible in Turkish, but they feel a little different.

• içeriyor = literally is including, but very often used in modern Turkish for a general present meaning: includes
• içerir = aorist/generic form, also meaning includes / contains

In many everyday contexts, Turkish prefers -yor forms where English would simply use the present simple.

So:

• Beceri rehberi olay yeri güvenliğini de içeriyor.
  very naturally means
• The skill guide also includes scene safety.

It does not have to sound temporary or progressive in English.

No. It comes from içermek, not içmek.

• içmek = to drink
• içermek = to include, contain

The verb here is:

• içer-iyor = includes / is including

So even though the beginning looks similar, it is a completely different verb.

Yes, it is completely normal.

The sentence follows standard Turkish word order:

• Beceri rehberi = subject
• olay yeri güvenliğini de = object + also
• içeriyor = verb

So the pattern is:

• Subject + Object + Verb

That is one of the biggest differences from English, where you would usually say:

• The skill guide also includes scene safety.

In Turkish, the verb usually comes at the end.

Yes, but moving de can shift the emphasis.

Here:

• olay yeri güvenliğini de içeriyor

means that scene safety is also one of the things included.

If you moved de to another element, the focus could change. Turkish uses de quite sensitively for emphasis.

In this sentence, its current position most naturally emphasizes that scene safety too is included.

Turkish does not have articles like English a/an and the.

Instead, Turkish shows specificity in other ways, especially through:

• word order
• context
• case endings, such as the accusative

So English may need:

• the skill guide
• scene safety

but Turkish simply says:

• beceri rehberi
• olay yeri güvenliğini

The meaning of definiteness or specificity is understood from the grammar and context rather than from separate article words.