There are some options:
1.) Kenpokan is very recommandable:
Their main focus is on martial arts, but they have a descent weightlifting equipment, kettlebells also!
On the other hand the membership is not very cheap.
2.) VfK Hannover:
That is a weightlifitng club, so weightlifting is their mainfocus... Powerlifting is also possible. Membership does not cost that much.
3.) SC Elite Hannover:
Also a sportsclub. Focus on powerlifting.
4.) Balance Fitness-Club:
Well, they got (still?) a squat rack. Changend it to a health-club, so I don't know if there still is a squat rack. No kettlebells.
Squatrack is there. Very cheap. Don't know if they got kettlebells.
6.) Atlantis Fitness-Center:
Squatrack. Membership is not that high.
I would recommand Kenpokan and the VfK Hannover.
Hope this helps!