is it possible to buy a bluethooth turkish keyboard for my macbook pro

I want to use my MacBook Pro to write in Turkish language without changing my MacBook Pro settings.

I'm not sure what you mean by that. You will always have to change your settings (namely in system preferences/keyboard/input sources, and then in the "flag" menu at the top right of the screen) if you want to write in Turkish, regardless of the hardware keyboard. You can type Turkish that way with the US keyboard too.

As for buying something, you just go to the Apple store website and see what they offer:

Unfortunately Turkish is not available. You could also contact retail Apple stores directly yourself and ask if a special order is possible, but I doubt they are available anywhere in the US.

Can I buy a blutooth Turkish (Qwerty) keyboard in USA?

PS You can also search Amazon for "turkish keyboard" and see what is available from sources other than Apple. They should also work with your macbook pro.

I want to use my MacBook Pro to write in Turkish language without changing my MacBook Pro settings.

That is Not the way the Mac works. Instead, it uses the 'all devices active' philosophy for keyboards and in many instances for pointing devices.

Based on that, you could literally type every-other keystroke using every-other keyboard. That works great when your second keyboard is a numeric keypad.

But Unless/Until you change the settings and select Turkish language (for ALL your keyboards at once) your Turkish keyboard will produce ENGLISH key codes.

There are no individual language/translation settings for individual keyboards.