I am looking for help with my new project, the idea behind is to make a mini model of a classroom with a automatic arm that controls a window. When the tempurature rises it will open and when the temperuter falls agin the window will close. 8)
And what kind of help do you want? It would be a lot easier if you post your code and ideas here. If you are looking for ideas - try Project Guidence. If you are looking for someone to do it for you - try Gigs and Collaborations where you can pay someone who will gladly code for you
I would like a code to open a window with a stepmotor
So, start writing one. We have no idea how you have connected the stepper motor to the Arduino, what kind of stepper it is, or how many steps it takes to open your window. Nor do we know whether you have limit switches to limit how far the window can open and close.
Your requirements sound like you go shopping for a jet engine to power your go cart with no more information than "it needs to use jet fuel".