how old should i have my female dachshunds fixed?

I most certainly wouldn't have them spayed until they've been in season at least one time, but that would depend on you and your ability to make sure they were kept away from all intact males for the full 3 weeks that they were in season, including not letting them outside to *potty* by themselves. If you have a busy life and can't manage the mess of the discharge or going out with them every time they need to go outside, then I'd have them spayed before they go into heat at all, meaning probably at around 6 months old, or a couple weeks before than. There are pros and cons to altering dogs, one of the pros of course is to eliminate the possibilities of an unwanted pregnancy with a b*tch, and also it prevents Pyometra, which can be a deadly uterine infection if left untreated. Of course, not all b*tches will ever get Pyometra, but if there's no uterus, then there can't be an infection of it, outside of the very rare *stump Pyometra.* (You can Google that if you wish) Again, a lot would depend on you and what you can and are willing to deal with. I've got an intact Dobe b*tch who's nearly 5 years old, and she'll never be bred. If she ever ends up with Pyometra, I'll cross that bridge if I ever come to it. The reason why I keep her intact is because Dobe b*tches are prone to spay incontinence, so if I were to have her spayed, there's probably at least a 90% chance she'd develop this, and then she's have to be on daily meds to control the urine leakage for the rest of her life. Spay incontinence can happen to any b*tch that's spayed, but again, it's common in my breed, but not common in all breeds or mixes.

Most would suggest, for a smaller dog, it's fine to get them done before the first season - by around 6 months. Some vets prefer to allow one season before spaying, but a lot of that would depend on whether you, as the owner, can be sure to keep her safe (as in confined) for the 21+ days she'll be in season and can cope with the mess - not that a smaller dog would be producing that much! Talk to your vet and take his advice.

six months

Before 6 months. Once they go into Heat some vets won't fix them and if they will it's an extra charge. 20$ more at my vet.

My vet did it when she was 6 months but when she came home she was very slow (my dog not my vet)

Yes.