How does the suffix -ki work? Thank you

 I will leave that to  the experts they seem to slip that little ki in all over the shop

but I think it can sometimes mean WHO, THAT, WHICH ,IS?????

http://www.turkishlanguage.co.uk/ki.htm

What does suffix -ki do?

1-It makes the word an adjective:

şimdi - now

şimdiki - present

and modifies the following word in time and space: 

şimdiki zaman - present time

dünkü gazete - yesterday´s newspaper

köşedeki ev - the house on the corner

2-It makes the word a pronoun:

benim - my

benimki - mine

You can answer the following question in two ways:

Q- Kimin arabası daha yeni? -whose car is newer?

A1 -Benim arabam - my car (long way)

A2- benimki - mine (short way)

We have another ki which is a word not suffix and written alone. It is used as conjunction and preposition. But because most of the natives don´t know which is which, you can see suffix -ki written alone and the conjunction ki added to a word. So, may Allah help a foreigner who still think that they can learn Turkish from those who don´t know how to distinguish -ki from ki, and -de from de and so.