when i installed my cintiq and started krita all works fine. With the tip I could draw and when I turn the pen over it change to erase mode and erased.

But now after newstart of my Pc Krita lost that settings don't know why. So I tried to change the settings but I'm totaly lost.

I don't know how to set the back to the erase mode and when i try to set the window with the color quick change, pen selction,...(don't know how it called thing is the prime mode) to one of the penkeys by settings it to left key I get the draw window put can not draw and by setting it to right key I can Draw and don't get the draw window.

can anybody held me?

Krita dos not switch to erase mode when using the erase side of the pen.
What Krita does, is assign one brush preset to each device (mouse, pen tip, pen eraser). And by default it starts with one eraser preset assigned to the pen eraser.
What you need to do is simply select one eraser preset with the pen eraser side and one painting preset with the pen tip side.
This is the way it works for Intuos Pro. I think it is the same with Cintiq.