I have a mini dachshund too. His name is Luke. Too be honest. He's either an idiot, or just really smart. He doesn't do anything but sleep, eat and beg for food. But we love him just as much. He's just different. I don't think he's really dumb, i just think he doesn't want to do anything because he doesn't have to. I've tried to teach him and he's just difficult, but i'm working on him. He's 6 almost 7 years old after all. He's been my girlfriends dog forever, but she never worked with him. He's really a good dog though. we can leave him while we're gone and he just curls up under his covers in his bed and sleeps! He submissively urinates. I can't stop this no matter what, but he's always done it. He's about the most low key dog i've ever seen, no toys, no playtime, nothing. just gets excited when he gets to go "bye-bye". Don't get me wrong, i really dont' think he's dumb. I know this because he won't beg from me, he knows i dont' like it, but he'll beg from my girlfriend. He's sneaky too, when he knows he's not supposed to have something, like wrigleys (our puppy) food, he'll wait til i leave the room and sneak over and try to get it! only i catch him in the act and he runs off like i'm gonna kill him! I wouldn't, don't worry.
He's pretty good with other dogs. but the bigger the dogs the more curious he his with them. He's not much of a play dog. My parents have 2 mini dachshunds. they don't like other big dogs(the didn't like wrigley, my weimaraner). But i think that might just be because they dont know them and maybe because they're smaller? Luke sure isn't that way, he thinks he's a big dog when he see's other dogs!
as far as excersize, the do need it, but you have to watch what they eat. Luke, or doxie is at a normal weight. And he doesn't get a walk everyday, just about 2 or 3 times a week. My parents dogs are really overweight and they walk twice a day! They eat alot of treats!
They are really loving dogs though. Sometimes they can be protective, but that's just because they love their owners. Not mean protective, just curious.
at least that's how mine are, but i've seen alot of dachshunds, and they all seem to be different to me. our neighbor has one and he doesn't get along with too many other dogs, but, with any dog, it's all about how much they've been socialized.
hope some of that helped!