Bu lezzetli kurabiyeleri görünce bir tane almadan edemiyorum.

Because kurabiyeleri is the definite direct object of görmek (to see) in the clause Bu lezzetli kurabiyeleri görünce.

Breakdown:

• kurabiye = cookie
• kurabiyeler = cookies
• kurabiyeleri = the cookies / these cookies (as a definite object)

In Turkish, a specific/definite direct object usually takes the accusative ending. Since the cookies are already identified by bu (these), they are definite, so -i is added:

• kurabiyeler
  • -i → kurabiyeleri

So this part means when I see these delicious cookies.

Bu itself does not change for singular and plural. It can mean this or these, depending on the noun.

So:

• bu kurabiye = this cookie
• bu kurabiyeler / bu kurabiyeleri = these cookies

English changes this → these, but Turkish keeps bu the same.

Because Turkish adjectives do not agree with nouns in number.

So:

• lezzetli kurabiye = delicious cookie
• lezzetli kurabiyeler = delicious cookies

The adjective lezzetli stays the same whether the noun is singular or plural.

Görünce means when (I) see, upon seeing, or once (I) see.

It comes from:

• görmek = to see
• verb stem: gör-
• suffix: -ince / -ınca / -ünce / -unca

Because of vowel harmony, it becomes:

• gör + ünce → görünce

This suffix makes a kind of time clause:

• gelince = when he/she comes
• bitince = when it finishes
• görünce = when he/she/I/you see(s)

In this sentence, the subject is understood from the main clause, so görünce here is naturally read as when I see.

Because this kind of Turkish subordinate clause often leaves the subject implicit when it is clear from context.

The main verb is:

• edemiyorum = I can’t

That tells us the subject is I, so görünce is understood as when I see.

Turkish often avoids repeating pronouns like ben unless they are needed for emphasis.

Bir tane means one, one piece, or one of them.

• bir = one / a
• tane = piece, item, unit

With countable objects like cookies, bir tane is very common and natural. It is a bit like saying:

• one
• one piece
• one of them

Here it stands for one cookie, so you do not need to repeat kurabiye.

You could also say:

• bir kurabiye almadan edemiyorum

But bir tane sounds very natural in everyday speech.

Because bir tane is being used as an indefinite object in bir tane almak.

In Turkish:

• definite/specific objects usually take the accusative
• indefinite/non-specific objects usually do not

Compare:

• Kurabiyeyi aldım. = I took the cookie.
• Bir kurabiye aldım. = I took a cookie.
• Bir tane aldım. = I took one.

In your sentence, the idea is I can’t help taking one, not that one specific cookie, so no accusative is used.

Literally, it is something like I cannot do without taking (one).

Breakdown:

• almak = to take
• almadan = without taking
• edemiyorum = I cannot do / I am unable to do

Together, -madan edememek is a very common Turkish pattern meaning:

• to be unable to refrain from doing
• to be unable to help doing
• to be unable to resist doing

So:

• almadan edemiyorum = I can’t help taking one / I can’t resist taking one

This is an idiomatic structure, and it is best learned as a pattern:

• Gülmeden edemiyorum. = I can’t help laughing.
• Bakmadan edemedim. = I couldn’t help looking.

Because the verb is etmek (to do), but when a vowel-initial suffix is added, the t often changes to d in pronunciation and spelling.

So:

• etmek
• ede-
• edemiyorum

This is normal:

• etmek → ediyor
• etmek → edemem
• etmek → edemiyorum

So edemiyorum is the correct form.

It can be understood as:

• ede- = do
• -miyor = not able / not doing in the present continuous negative form
• -um = I

More simply, treat edemiyorum as:

• I can’t do
• I’m unable to do

In this sentence, it combines with almadan to form the idiom almadan edemiyorum.

Turkish often puts the time/background clause first and the main verb at the end.

So the structure is:

• Bu lezzetli kurabiyeleri görünce = When I see these delicious cookies
• bir tane almadan edemiyorum = I can’t help taking one

This is very natural Turkish word order. The verb usually comes at the end of its clause, and extra information like time or condition often comes first.

Yes. That is a very natural English translation.

The Turkish structure -madan edememek often corresponds to:

• can’t help doing
• can’t resist doing
• can’t refrain from doing

So all of these are good ways to understand it:

• When I see these delicious cookies, I can’t help taking one.
• When I see these delicious cookies, I can’t resist taking one.

Yes, but the nuance changes slightly.

• görünce = when I see / upon seeing
• gördüğümde = when I see / when I saw them in that situation / when it is the case that I see them

In many contexts they can both work, but görünce is often a little more immediate and event-like: as soon as I see them / whenever I see them.

So in this sentence, görünce sounds very natural and idiomatic.

It sounds like a habitual or repeated reaction, even though the verb is in the present continuous form.

• edemiyorum literally looks like I am not able
• but in Turkish, the present continuous can also describe a regular personal tendency

So the sentence means something like:

• Whenever I see these delicious cookies, I can’t help taking one.

It is not limited to one single moment right now.