I really doubt the CDU will win a single Hamburg district.
The CDU won the last mayoral election in Hamburg.
You fell into the trap!
Just because a locality votes for one party in a local election doesn't imply that the same locality will vote for the same party in a 'national' election.
It would be admitting that, because Rhode Island (a state very similar to Hamburg) elected a Republican governor and a non-Democrat mayor of Providence, that RI will vote -R for its two congressional districts.
If there's a CDU landslide, several districts could be in play.
If there's a moderate CDU victory, they have a fair chance in the wealthy suburbs. In 1994, for example the CDU won Hamburg-North. (Of course, with a conservative southerner like Stoiber as candidate the chance would be very low.)
