Unfortunately the code does not work. There's always a "0" returning.
Which one? Mine? That wasn't intended to work, it was just an example. For example the address was just a random number. You have to modify or at least provide a link to the datasheet of your device, so we have a chance to get the necessary information.
Where do I have to write the control bytes?
The control bytes are the address plus read/write bit, so they are in the code already.
And how can a repeated start be done?
Does that mean a start condition without a stop condition? Else you have to define it.