Yes, there are many human foods that can be toxic or dangerous for German Shepherd Dogs to eat. Here are some of the most common ones:

1. Chocolate: Chocolate contains theobromine, which can be toxic to dogs. Dark chocolate and unsweetened baking chocolate contain higher levels of theobromine than milk chocolate and can be more dangerous. Signs of chocolate poisoning in dogs can include vomiting, diarrhea, increased thirst, restlessness, and in severe cases, seizures and death.
2. Grapes and Raisins: Grapes and raisins can cause kidney failure in dogs. Even small amounts can be toxic, and the exact toxic dose is not known. Symptoms of grape and raisin toxicity can include vomiting, diarrhea, loss of appetite, and abdominal pain.
3. Onions and Garlic: Onions and garlic contain compounds that can damage a dog’s red blood cells and cause anemia. Garlic is considered to be more toxic than onions, but both can be dangerous if consumed in large amounts. Symptoms of onion and garlic toxicity can include vomiting, diarrhea, pale gums, weakness, and breathing difficulties.
4. Avocados: Avocados contain persin, a fungicidal toxin that can cause vomiting and diarrhea in dogs. Ingestion of large amounts of avocado can also lead to more serious symptoms such as fluid accumulation in the chest and abdomen, breathing difficulties, and heart problems.
5. Alcohol: Alcohol can be toxic to dogs and can cause symptoms such as vomiting, diarrhea, decreased coordination, central nervous system depression, difficulty breathing, and in severe cases, coma and death.
6. Xylitol: Xylitol is a sugar substitute that is commonly found in sugar-free gum and candy. It can cause a rapid release of insulin, leading to hypoglycemia (low blood sugar) in dogs. Symptoms of xylitol poisoning in dogs can include vomiting, loss of coordination, seizures, and liver failure.
7. Fatty Foods: Fatty foods, such as bacon, sausage, and fatty meats, can cause pancreatitis in dogs. Pancreatitis is a serious condition that can cause vomiting, diarrhea, abdominal pain, and in severe cases, death.
8. Macadamia Nuts: Macadamia nuts can cause vomiting, diarrhea, weakness, depression, tremors, and hyperthermia in dogs. The exact toxic dose of macadamia nuts is not known, and symptoms can occur within 12 hours of ingestion.

It is important to remember that dogs have different nutritional needs than humans and not all human foods are safe for them to eat. To keep your German Shepherd Dog healthy, it is best to stick to a balanced and nutritionally complete commercial dog food diet, and avoid giving them any human foods unless they are specifically designed for dogs and approved by a veterinarian.