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First, 6 weeks old is awful young to allow a pup, especially a giant breed, to be away from her momma and littermates. There is so much they learn between 6 and 8 weeks that is pretty important for development. You can teach her these things, but you have to be pretty relentless in doing so. Teaching her manners is really important...like not biting and mouthing. So if she does these things, nip it in the bud and do not allow it righht from the begining. :)
The little bit of blood and mucous can be anything from intestinal parasites, stress from a new home, and commonly, parasites. If you are feeding a different food than the place she came from, that can also cause the digestive upset. Feed her a bland meal of boiled chicken and rice to help settle down her tummy and have a fecal test done to check for parasites. The vet can worm her and in a few days she should be back to normal if there are parasites present. If you changed her food, then the chicken and rice will help and then you can wean her onto the kibble of your choice over the course of 5 days. :)
If it is caused by the stress of a new home/surroundings, it should get better over the next couple of days but you want to rule out parasites first.
Good luck with your girl and remember, when she has all of her shots, socialization is very very important with this breed. :)