When teething begin at 4 months of age, puppy tends to chew on anything they can get hold of. It’s very normal. They bite/nip naturally to relieve their itching gums and jaw. Keep If she bit on your arm, say “ouch” and teach her that’s not good, then hand her a chewing toy. It will eventually go away when their adult teeth come in.
A German Shepherd’s ears usually stand up on their own between 8 weeks and 5 months of age. During this period, one day they’re up and the next day they’re down. The teething is also competing for the calcium that makes her ears stand. You can help her to use her ear muscle by making funny noises to perk up her ears. Some owners also suggest giving her yogurt as a snack. Do not massage her ears because it might even hinder the development of her muscle.