Male sheltie and female Dachs? Will there be a problem with sheltie trying to mate?

No, no, you're totally right

 

In attempts to stay on topic here...

You may have your hands full at first with unaltered pets, but as long as proper precautions and diligence is taken, it will work out fine

 

Animals are not very selective. Your sheltie will very likely breed the dachshund and she will probably help him out. That's why there are so many "designer" breeds out there. If the dachsy does get impregnated she could have a terrible time trying to whelp the pups.
It's too bad you can't spay or neuter one of them. There is higher likelihood of mammory cancer, metritis and pyometra for the bitch. Prostrate problems, infections and behavioural problems are seen more in the males. I spayed all my girls once they were finished in the breeding program. I was never plagued with incontenence in any of our bitches even when many of them were 16 plus of age although I know it can happen. I think it is more likely to happen when she spends a lot of her life holding her urine for too long - just as it does in woman. Once the estrogen depletes there is nothing to condition the bladder and all the stretching over the years has a bad effect.

 

Just FYI- altering dog IS NOT Common in Europe. Most dogs are unaltered. I would not say exactly for Norway but many countries will charge you arm and leg for this procedure and it will be difficult to find a vet to do the procedure to begin with. Cost is usually around $1500