Cats Need to Stretch and Scratch
Evidence shows declawing is inhumane and it can cause health issues for your cat later in life, such as arthritis, paw pain, and back pain. Most veterinarians in the US will not perform the procedure and the practice has been outlawed in many other countries. But you can give your cat a better outlet than scratching your furniture and you can use deterrents.
There are many different products available to protect your furniture. Try double-sided tape made for furniture protection or a more permanent solution like a scratch guard.
Provide an appropriate outlet for your cat. Most cats like to have both pads and posts so they can scratch and stretch in different positions.