While chewing is a purely instinctual act for dogs, excessive chewing can be destructive. Dogs may bite on the cushions and pillows. They may even chew your personal items. There might be various underlying reasons for this behaviour.
Your dog may be doing it because of teething, out of boredom, or simply because they have excessive energy. Puppies especially tend to bite out of curiosity.
This can be controlled. When you catch your dog chewing something forbidden, be quick to grab their attention with a stern voice and replace the object with a chew toy.
Ensure that your dog has no access to your personal items to avoid damages. Secondly, ensure that they have plenty of chew toys to play. Thirdly, get your dogs to exercise enough to wear off the excessive energy.