The responsible office in Saxony is the school authority LASUB. They have a department for the recognition of school certificates in Bautzen. Here is the website:
Here is the form to apply to have your school certificate recognised:
On page 5 it lists the documents which are to be sent along with the form.
The school certificate itself and the translation of it have to be sent as copies. However, the copies have to be made officially.
I could not find any information about the cost. In Berlin, for example, it costs 55 euro.
I cannot give you any specific information about how long it takes; I have heard, however, that it can be quite a lengthy process. Therefore I recommend you submit the application sooner rather than later. The contact number on the website may be able to provide more detailed information.
In Leipzig there are special youth advisory services called JMD for migrants that can assist you with this. If you are under the age of 27, you can contact one of them:
The Welcome Centre is also a useful place to get information: