Ağabey, şu köşede hangi dolmuşun durduğunu bir sorsana.

Ağabey literally means older brother, but in everyday Turkish it is also used to address a man in a friendly, familiar way—something like brother, bro, or sometimes mate/man depending on context.

In this sentence, it is being used as a form of address at the beginning, like calling out to someone before making a request.

A few useful notes:

• It is often shortened in speech to abi.
• It is informal.
• It does not necessarily mean the person is your actual brother.

Turkish has a three-way distinction here:

• bu = this, near me
• şu = that/this one there, usually visible, often being pointed out
• o = that one over there / that one already known

So şu köşede suggests something like at that corner there or at this corner right there, often with the speaker mentally or physically indicating it.

For learners, şu is very common when talking about something visible and specific.

A dolmuş is a very common type of shared public transport in Turkey. It is usually a shared minibus or sometimes a shared taxi that follows a set route.

There is no perfect one-word English equivalent, so it is often just left as dolmuş in explanations.

In this sentence, the speaker is asking about which dolmuş stops at that corner.

The ending -de is the locative suffix, meaning in, on, or at.

• köşe = corner
• köşede = at the corner / on the corner

So:

• şu köşede = at that corner

This is a very common suffix in Turkish:

• evde = at home
• okulda = at school
• masada = on the table

Because this sentence contains an embedded clause:
hangi dolmuşun durduğunu = which dolmuş stops there

In Turkish, when you make a clause with -DIK (here durduğu / durduğunu), the subject of that clause usually takes the genitive ending.

So:

• dolmuş = dolmuş
• dolmuşun = of the dolmuş / the dolmuş's

But here that genitive is not showing possession in the usual English sense. It is part of the grammar of the embedded clause.

A parallel example:

• Ali'nin geldiğini biliyorum = I know that Ali came / is coming

Here:

• Ali'nin is the subject of the embedded clause
• geldiğini is the nominalized verb

So in your sentence:

• hangi dolmuşun durduğunu = which dolmuş stops

This is one of the most important pieces of the sentence.

Breakdown:

• dur- = to stop / stand
• -duk / -dık / -diği type form = a nominalizing suffix that turns a verb into a noun-like clause
• -u = a possessive ending here
• -nu = accusative marking on the whole clause

So durduğunu is part of the structure meaning something like:

• that it stops
• its stopping
• in natural English here: which dolmuş stops there

More precisely:

• durduğu = that it stops/stopped
• durduğunu = the same clause, but marked as the object of sormak (to ask)

That is why the whole phrase works as the thing being asked about:

• hangi dolmuşun durduğunu sormak
  = to ask which dolmuş stops

A key point: even though it looks a bit like a past form, this structure does not simply mean past tense here. In these embedded clauses, it often corresponds to English which one stops / is stopping / has stopped, depending on context.

Because hangi already makes it a question word structure.

In Turkish, question words like these do not normally combine with mi:

• kim = who
• ne = what
• hangi = which
• nerede = where

So:

• hangi dolmuşun durduğunu = which dolmuş stops

Not:

• hangi dolmuşun mu durduğunu ✘

The particle mi is typically used for yes/no questions, not for wh-questions.

Here, bir does not literally mean one.

In colloquial Turkish, bir is often used with imperatives and requests to soften them or make them sound more casual, like:

• bir bak = just have a look
• bir gelsene = come here for a sec
• bir sor = just ask

So bir sorsana means something like:

• just ask
• go ask for a second
• why don't you just ask?

It makes the request sound more natural and conversational.

Sorsana comes from sor (ask) plus -sana, which adds a tone like:

• come on, ask
• why don't you ask?
• just ask

It is usually:

• informal
• often friendly
• sometimes slightly insistent, depending on tone of voice

So it is not automatically rude, but it is definitely casual. You would use it with someone you know well, or in relaxed everyday speech.

A more neutral or polite version might be something like:

• bir sorar mısın? = could you ask?
• bir sorar mısınız? = could you ask? (polite/plural)

Because Turkish normally puts the main verb at the end.

The thing being asked about comes before the verb:

• şu köşede hangi dolmuşun durduğunu = what is being asked
• bir sorsana = ask

So the structure is basically:

• [that-corner-at which dolmuş stops] [ask]

This is very normal Turkish word order.

You could think of it as:

• Ağabey, [şu köşede hangi dolmuşun durduğunu] bir sorsana.

That whole bracketed part is the object of sormak.

Yes, it sounds quite natural and conversational.

What makes it sound everyday and colloquial:

• Ağabey as direct address
• şu for a visible place
• bir as a softener
• sorsana as an informal request

So this is not stiff textbook Turkish. It sounds like something someone might really say in casual speech.

If you wanted a more formal version, you might say something more like:

• Şu köşede hangi dolmuşun durduğunu sorar mısınız?

But the original sentence is much more conversational.