Hi OK,
Tower and Approach have been separated some years ago. So we have specialized Approach controllers and specialized Tower controllers.
Here is a announcement for Tower jobs:
Job announcement
However I dont know for which towers they are searching exactly. But as Frankfurt and Munich both are intended to get a additional runway and therefore need more controllers, there is quite a good chance that you'll be assigned to one of those.
There are two employer for tower jobs in Germany. The DFS (all international hubs) and the Tower Company.
The Tower Company is actually a subsidiary company of the DFS and is working a lot of the smaller airfields in Germany.
However the payment and working conditions in the Tower Company are not as good as in the DFS.
The controllers within the DFS are paid the same regardless of tower or center. The only difference are the working hours. You have to work less the more traffic you have to handle.