It´s a rule that never failed me. I mean I was never corrected when I followed it. When I refer behind my back I use bu.

I guess this means in a simple way that whenever we say in English "this" in a sentence we will us "bu" and whenever we say "that" we will use "şu", no matter we´re pointing for something or just talking about something..righ?

It´s not that simple, Bambib, but it´s a good start.

can´t you lie to me I convinced myself that´s it is easy .....the grammer is very difficult. now I feel  that it will take me ages to understand

şu: that

bu: this

Normally ´Şu´ is used for objects and not people, it is possible to use ´şu´ for human but only with another word that shows its a human. for example:

"Şu adam" : "that man"

You might need this too, "bu, bunlar" is for people and objects near/close to you.

"şu, şunlar" for objects far from you.

Another example:

We say "şu araba" : "that car" when its distance from us, and we´re just pointing on it from far.

But if the car is right in front of us it is "bu araba"

i learned this before, from here; and i hope it helps you.

I have a feeling Turks when speaking English are using this too much in abstract contexts, in places where that or it would sound more normal to me. I guess it is because of this reference to mentioned things.