Solution applied:
private void ShowByCoordinates(Window window, int screenId, int LeftTransform, int TopTransform){
System.Drawing.Rectangle bounds = System.Drawing.Rectangle.Empty;
System.Windows.Forms.Screen s0 = System.Windows.Forms.Screen.AllScreens[screenId];
bounds = s0.WorkingArea;
window.Left = bounds.X + LeftTransform;
window.Top = bounds.Y + TopTransform;
window.Show();
}
It was pretty simple but I was conviced to set the working area or stuff like that.