Dolmuş beklerken bir bisküvi daha yedim.

Because Turkish normally puts the main verb at the end of the clause. A very common neutral order is:

time/context + object + verb

So:

Dolmuş beklerken = while waiting for the dolmuş
bir bisküvi daha = one more biscuit
yedim = I ate

This end-of-sentence verb placement is one of the biggest word-order differences from English.

-ken means while or when and links two actions happening at the same time.

So beklerken means while waiting / when I was waiting.

In this sentence, it shows that the eating happened during the waiting.

Because -ken usually attaches to a verb form, not directly to the bare dictionary stem.

Here the form is:

bekler + ken → beklerken

This is the usual way to say while waiting. Historically it is related to bekler iken, which got shortened.

For learners, the important point is simply:

• beklemek = to wait
• beklerken = while waiting

Turkish often drops subject pronouns when the verb ending already shows who is doing the action.

Here, yedim breaks down as:

• ye- = eat
• -di- = past tense
• -m = I

So yedim already means I ate, and ben is unnecessary unless you want extra emphasis.

Because Turkish often uses a bare object when it is non-specific or understood more generally.

So:

• dolmuş beklerken = while waiting for a dolmuş / while waiting for the dolmuş in a general, natural sense
• dolmuşu beklerken = while waiting for that specific dolmuş

Both can be possible, but the version without -u sounds very natural in everyday Turkish when the object is not being treated as a specifically identified one.

Because bir bisküvi is an indefinite direct object: a biscuit / one biscuit.

In Turkish, direct objects usually take the accusative ending only when they are definite or specific.

So:

• bir bisküvi yedim = I ate a biscuit
• bisküviyi yedim = I ate the biscuit
• bir bisküviyi yedim can exist in some contexts, but it makes the biscuit sound specific

In this sentence, the meaning is just one more biscuit, so no accusative is needed.

Here daha means more, and together with bir bisküvi it gives the meaning one more biscuit / another biscuit.

So:

bir bisküvi daha = one more biscuit

This is a very common pattern:

• bir kahve daha = one more coffee
• iki dakika daha = two more minutes
• bir soru daha = one more question

In this meaning, Turkish commonly uses:

bir + noun + daha

So bir bisküvi daha is the normal way to say one more biscuit.

If you move daha, the sentence may sound unnatural or the meaning may change. For example, bir daha often means again or ever again, which is a different idea.

So here, bir bisküvi daha is the correct and natural phrase.

Yes, unless Turkish clearly gives a different subject, the usual understanding is that the subject of beklerken is the same as the main clause subject.

So this sentence is naturally understood as:

While I was waiting for the dolmuş, I ate one more biscuit.

If the subject were different, Turkish would usually make that clear:

• Ali dolmuş beklerken bir bisküvi daha yedim.
  = While Ali was waiting for the dolmuş, I ate one more biscuit.

Yes. Turkish word order is flexible, but different orders change the focus or emphasis.

The given sentence is very natural and neutral:

Dolmuş beklerken bir bisküvi daha yedim.

You could also say:

• Bir bisküvi daha dolmuş beklerken yedim.

But that sounds more marked and less neutral. Learners should usually stick with the original order unless they have a reason to emphasize something specific.

Yedim is the simple past in Turkish, formed with -DI.

Breakdown:

• ye- = eat
• -di = past tense
• -m = I

So yedim = I ate.

In English, depending on context, it can sometimes feel close to I was eating or I had a biscuit, but the basic form is the straightforward past: I ate.