A dog in good physical condition and with good musculature is able to perform normal everyday activities. There are many opinions about stair climbing of dogs, especially dachshunds, but little established knowledge.
Remember, your Dachshund is a dog and needs to be able to live and enjoy life as a dog. Too much protection and "wrapping him in absorbent cotton" to avoid back problems is not fun or even useful for you or your dog.
On the other hand, it would certainly not be fair to let a somewhat stronger standard dachshund always and constantly run down a steep staircase (especially down). As the owner, therefore, you must consider for yourself. Please take into account that the weight of the dog is not evenly distributed on all four paws. Even when standing horizontally, 2/3 of the total weight rests on the front legs.
If you have an overzealous dog that gets on tables or window sills and jumps down from them, this must be stopped.
Link Tip:
Jumping and Stairs [UK Dachshund Breed Council]