Ours is the same way. We don’t have a cat, but my mother in law has another mini dachshund that is 14 and he will play with Cooper but only for so long and then he is not interested and will growl at him, but Cooper never learns.
It took forever for Cooper to learn to use the steps. We tried to get him to go after treats and stuff but he would never do it. It was kind of nice because we didn’t have to use gates to keep him on the first floor, but then one day we just found him upstairs in the bedroom, so I guess he figured it out on his own.
We don’t really do anything at this point. He is still a puppy and in pretty good shape so we just jumps around all over the place. We put a chest at the end of our bed so that he just has a step down to that and then a step down to the ground, but he still jumps off of the couch all the time. With the 14 year old, he has trouble jumping, so he will come over to the couch and just kind of look at you and that is when you know he wants up. And then if he is on the couch and stands up and gets close to the edge we help him down. But sometimes he jumps on his own.
Edit: Oh yeah and the ramps don’t really work. My wife’s grandpap made a ramp for the 14 year old to use when he goes up the steps to the deck (like 2 steps) when he comes inside from going to the bathroom and he just goes right around it. He made a nice carpeted ramp so that the dog could just walk up it and the dog ignores it and jumps up the steps. I think dachshunds might just be too dumb 