Correct me if I'm wrong, but I presume it is because Kuşadası means island of the bird. So therefore it is a simple noun which has already been suffixed.

So normally we would use the suffix -a, -e for to, towards, and the buffer letter -y to become -ya, -ye - when it is added onto a root word ending in a vowel.

So for example, if you're saying "to the bank" - you would write bankaya. As the buffer letter y is used with this noun because it has not already been suffixed.

But when an already suffixed noun is in question - you have to use the buffer letter -n, therefore -ne, -na when it is added as a second suffix.

So therefore to go to "his bank" (bankasıit is bankasına - to his bank. Therefore, in the case of "to go to Kuşadası" as it is already suffixed, we would write Kuşadası'na.

I hope that makes some semblance of sense!

How about this: buffer -n- appears after a suffix is added to the possessive suffix?

Yes, I agree with Daydreamer. I think it is like I tried to say before, except I missed out in this instance, - is it because you use the buffer letter -n, for a word which already has a possessed ending. And in this instance.. the island belongs to the bird

Thanks. That made a lot of sense. As for your next question - I am answering this quickly without much thought, so doubt it will be the answer you are looking for - but is it that you use -n as a buffer with the personal pronouns bu, şu and o?

If you are looking for another answer, I shall put my thinking cap on later

Thank you Salukvadze. Your questions were useful, as they got my mind thinking again