Hi MoazSh,
In Germany it's normal to go to school for 12-13 years to get your "Abitur". With this you can go to university. I think it depends on how fast you can learn German and the stuff for your "Abitur".
In the most schools you will start with the 10th grade, as everything from that point is relevant for your "Abitur".
Hope this can help, Mirco