[Leczyslaw]

Isn't Dachshund German? :P

Yes, which is why it isn't pronounced like that.
here I'm terrible at explaining

This dude explained it half decently

Living in Austria (German speaking) the actual way to pronounce it would be with the German "ch" sound which takes some time to perfect. It is kind of guttural sounding.
It doesn't sound anything like Dash-hound or Dash-hund.
The beginning sound (Da) is pronounced like it looks Dah. And then the guttural "ch" sound with an "s". Hund - hoond.
There is no real English equivalent for the "ch" sound. The closest would be Dahx-hoond. I hope somehow that makes some sense to somebody.
Dachs - badger Hund - dog.
And another bit of trivia: Hardly anyone in Germany or Austria calls it a Dachshund (even though that is where the name came from!). The common name here is either a Dackel or a Teckel. Dachshund - Definition and More from the Free Merriam-Webster Dictionary