Wow that is so young
Be sure to keep your puppy hydrated. Are the gums pink? You might need to rub a little syrup on the gums to keep the blood sugar up. Definitely take your puppy to the vet as soon as they are open because such a young puppy can go downhill so fast. I'm not familiar with Greece, but parvo is a huge concern with young unvaccinated puppies here and blood in the stool is a symptom.
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~Magnifique Yorkies~
Purchasing from backyard breeders, pet shops, and puppymills perpetuates the suffering of other dogs.
Educate yourself and buy from reputable breeders or rescue.