A lot of people don't let their daschunds go up and down stairs or jump up on furniture to prevent back injury.
I let mine do stairs and jump up on the bed and stuff if he wants to. Is this bad?

Stairs shouldn't be too much of an issue.
Jumping however should be avoided.

Make or guy a small set of stairs so he can walk up them to your bed.
My mother in law bought some for her old yorkshire terrier because she has arthritis :)