Turnikeden geçer geçmez sağdaki perona git; yanlış perona inersen aktarma zor oluyor.

Turnikeden = turnike + -den.

• turnike = turnstile
• -den = the ablative ending, often meaning from, out of, or sometimes marking the thing you pass through

So turnikeden geçmek means to pass through the turnstile.

In English we usually say through, but Turkish often uses this structure with geçmek.

This is a very common Turkish pattern:

• geçer geçmez = as soon as (someone) passes
• literally it looks like the verb is repeated in two forms, but together it acts like a fixed expression meaning immediately after

You will see the same pattern in many other phrases:

• gelir gelmez = as soon as he/she comes
• biter bitmez = as soon as it ends
• duyar duymaz = as soon as he/she hears

So Turnikeden geçer geçmez... means As soon as you go through the turnstile...

Yes, but the nuance changes a little.

• Turnikeden geçince = when/after you pass through the turnstile
• Turnikeden geçer geçmez = as soon as you pass through the turnstile

So geçer geçmez is more immediate and stronger. It suggests don’t wait; do it right away.

Sağdaki comes from:

• sağ = right
• sağda = on the right
• sağdaki = the one that is on the right / the one on the right side

The ending -ki turns a location expression into something like the one located there.

So:

• sağdaki peron = the platform on the right

You can compare:

• soldaki kapı = the door on the left
• arkadaki araba = the car in the back
• öndeki masa = the table in front

Because gitmek normally takes the dative case when you go to a place.

• peron = platform
• perona = to the platform

So:

• eve gitmek = to go home
• okula gitmek = to go to school
• perona gitmek = to go to the platform

That -a / -e ending is very common after motion toward a destination.

Git is the singular informal imperative of gitmek: go.

So the sentence is speaking directly to one person in an informal way:

• git = go
• gidin = go (plural or polite)
• gidiniz = very formal / less common in everyday speech

So sağdaki perona git means go to the platform on the right.

Because Turkish usually does not need subject pronouns when the verb ending already shows the subject.

Here:

• git already tells you it is a command to you
• inersen means if you get off / if you go down, and the -sen part shows you

So Turkish often leaves out sen unless it wants emphasis or contrast.

İnersen comes from inmek + conditional -se/-sa + -n for you:

• inmek = to go down, get off, descend, alight
• inersen = if you get off / if you go down

In transportation contexts, inmek is often used for:

• getting off a bus, train, metro, etc.
• going down to a platform or lower level

So yanlış perona inersen means something like:

• if you go down to the wrong platform
• or if you end up on the wrong platform

Because inmek often takes the dative when it means movement onto / down to a place.

• perona inmek = to go down to the platform
• peronda = on the platform

So:

• yanlış perona inersen = if you go down to the wrong platform
• yanlış peronda... would describe being on the platform, not the motion of going there

This is one of those verb-and-case combinations that learners need to memorize.

Aktarma means transfer, changing lines, or making a connection in transport.

For example:

• aktarma yapmak = to make a transfer
• aktarma merkezi = transfer hub

In this sentence, it refers to changing from one line/platform to another.

Aktarma zor oluyor sounds natural and conversational. It means something like:

• the transfer becomes difficult
• transferring gets difficult
• it ends up being hard to transfer

Why oluyor?

• zor = difficult
• olmak adds the sense of becoming / turning out to be
• oluyor can sound more practical, experiential, or descriptive of what usually happens in real life

Compare:

• Aktarma zor. = The transfer is difficult.
• Aktarma zor olur. = The transfer will be / tends to be difficult.
• Aktarma zor oluyor. = Transferring becomes difficult / it gets difficult.

In spoken Turkish, zor oluyor is very common.

It is quite natural Turkish word order.

The sentence is structured like this:

• Turnikeden geçer geçmez = as soon as you pass through the turnstile
• sağdaki perona git = go to the platform on the right
• yanlış perona inersen = if you go down to the wrong platform
• aktarma zor oluyor = transferring gets difficult

Turkish often puts time clauses and condition clauses before the main point:

• When X happens, do Y
• If X happens, Y becomes difficult

So the order is very normal and easy for a Turkish speaker to process.