Yedekleme dosyasını silmeden önce iki kez kontrol ettim.

A natural breakdown is:

• yedekleme = backup / backing up
• dosyasını = the file (as a definite direct object)
• silmeden önce = before deleting
• iki kez = twice / two times
• kontrol ettim = I checked

So the sentence structure is basically:

[the backup file] [before deleting] [twice] [I checked]

Turkish usually puts the main verb at the end.

Because this is a Turkish noun compound.

In many Turkish compounds, the first noun stays plain, and the second noun takes a compound ending such as -ı / -i / -u / -ü or -sı / -si / -su / -sü.

So:

• yedekleme = backup / backing up
• dosya = file
• yedekleme dosyası = backup file

This pattern is very common in Turkish. Similar examples are:

• elma suyu = apple juice
• öğrenci kimliği = student ID
• telefon numarası = phone number

So yedekleme dosyası is the normal Turkish way to say backup file.

Because the whole noun phrase is the definite direct object of the verb kontrol ettim.

The base compound is:

• yedekleme dosyası = backup file

But since the speaker means a specific backup file, Turkish adds the accusative ending:

• dosyası
  • -nı → dosyasını

So:

• yedekleme dosyası = a backup file / backup file
• yedekleme dosyasını = the backup file, as the object of the verb

The -n- is a buffer consonant. It appears because the noun already has that compound/possessive-style ending -sı.

A useful way to see it is:

• dosya-sı-nı

Silmeden önce means before deleting.

It is made from:

• silmek = to delete
• silme = deleting
• silmeden = without deleting
• silmeden önce = before deleting

This is a very common Turkish pattern:

• gitmeden önce = before going
• yatmadan önce = before going to bed
• konuşmadan önce = before speaking

So even though -meden / -madan by itself often means without doing, when it is followed by önce, the whole expression means before doing.

In Turkish, it is better to think of önce as a postposition, not a preposition.

English says:

• before deleting

Turkish says:

• silmeden önce
• literally: deleting-before

So the word that means before comes after the thing it relates to. That is very typical in Turkish.

Because Turkish often leaves pronouns out when the verb already shows the person clearly.

Here the verb is:

• kontrol ettim

The ending -im tells you the subject is I.

So kontrol ettim already means I checked.

If you add ben, it becomes more emphatic:

• Ben kontrol ettim = I checked it

But in a neutral sentence, Turkish usually omits ben.

Because kontrol etmek is a very common compound verb in Turkish.

Turkish often takes a noun, including borrowed nouns, and combines it with etmek to make a verb.

So:

• kontrol = check / control
• kontrol etmek = to check

Then in the past tense:

• kontrol ettim = I checked

This pattern is extremely common. For example:

• yardım etmek = to help
• fark etmek = to notice
• kabul etmek = to accept

So kontrol ettim is completely normal Turkish.

It is the simple past (also often called the definite past).

Breakdown:

• et- = do
• -ti = past tense
• -m = I

So:

• ettim = I did

And with kontrol:

• kontrol ettim = I checked

It refers to a completed action in the past.

İki kez means twice or two times.

Yes, Turkish has other common ways to say this:

• iki kez
• iki defa
• iki kere

All three are very common. In this sentence, iki kez kontrol ettim simply means I checked it twice.

Because Turkish normally prefers subject-object-verb order, and the main verb often comes last.

In this sentence, the most neutral order is:

• Yedekleme dosyasını silmeden önce iki kez kontrol ettim.

Very literally:

• The backup file before deleting twice checked-I.

That sounds strange in English, but it is normal in Turkish.

Turkish word order is flexible, though. You can move parts around for emphasis, as long as the sentence still sounds natural. For example:

• Silmeden önce yedekleme dosyasını iki kez kontrol ettim.

This still means the same thing, but the focus shifts a little.

Not always, but in this sentence that is the most natural interpretation.

Here, no different subject is mentioned inside silmeden önce, so the usual reading is:

• I checked the backup file twice before I deleted it.

However, Turkish can make the subject different if it is stated clearly. For example, a sentence could explicitly mention another person before silmeden önce.

So the rule is:

• if no other subject is given, readers usually infer it from context, often the same subject as the main verb
• if a different subject is needed, Turkish can state it

Grammatically, it is the object of kontrol ettim.

The main verb of the sentence is kontrol ettim, so:

• Yedekleme dosyasını kontrol ettim = I checked the backup file

The phrase silmeden önce is an adverbial clause telling when that checking happened:

• before deleting

Semantically, the same file is also understood as the one that would be deleted, but the direct grammatical object of the main clause is tied to kontrol ettim.