In general, Universities/international offices do not directly help to find apartments for foreign students. The key actors in this context are the local student unions (“Studentenwerke”).
On the website of the DAAD, there is an entry “Finding accommodation” with comprehensive information in English in the section “Information for Foreigners” [Link]. Here you will find both the addresses of the student unions as well as a database “accommodation finder”, where you can filter by city and type of accommodation. This information and database are not only available for DAAD scholars but for all those who wish to study in Germany. There is also a link to this database on the website “Study in Germany” [Link].
The student unions assist in finding accommodation. On the website contact person with local phone numbers are indicated which the student can call (for example, in Bonn). Specific advice can therefore best be given by the student unions on site.