I would like to know in which case we use gelmekteyim

Is that "I saw in" ??? Like I saw in your eyes..or more creepily...I saw in your window?

more like: I'm on my way
gelmek- to come

here -te/-de is "at the act of".
It can simply be translated as present continuous tense.
I am coming. (gelmek)
I'm on my way. (gelmek and gitmek depending on the situaiton)

Thank you for the replies but what I meant is that I know this word is not common but I would like to know if you heard that before and where was that??? In a letter, in the news, or in the litterature??? Do some people use it in daily conversation?

thanks in advance! : )

Yes! It is used daily. Usually when someone telephones you cos you are late and you say "gelmekteyim" as a reply.

It is ALWAYS used by my local pizza company when I ask why I am still waiting for my order! (Gelmekte or yolda)