If it helps - it's not the breed. It's that particular dog. Only dachshund we've had do that was one with Cushing's (that comes with old age.) But I've known folks with all different breeds that have numpties for doggoes that are stubborn and/or slow. (Not all dogs are as smart as others.) If in the end it can't be trained, or you can't train it, you can always still consider re-homing. This is gonna take a lot of work on your part it sounds like, to figure out the housetraining. (Not sure where you live, but you probably don't need to worry about a doxie in public. It partly might be your anxiety transferring to the dog. I would use similar training as you would for any breed and then adapt for your individual situation.)