Nervous, stressed, escaping, unhappy hamster

[Lovehearts]

I bought a Syrian hamster, lovehearts nearly 3 weeks ago from the pet shop. I gave her 3 days to settle in her cage and then started to introduce my smell by giving her treats, I’ve had her in the bath tub trying to hold her and she goes around in her ball. In her cage she has chew toys I put fresh fruit hidden in the cage, a wheel and 2 levels. However she is extremely nervous, very jumpy and flys out of your hand when handled and bits a lot! She continually chews the bars on one side of her cage, she has even chewed through a plastic tube in her cage and escaped! She just seems so unhappy I feel awful to be keeping her in a cage but she is so scared to be handled to enjoy being out of the cage. I’m really stuck on how to improve her wellbeing, any advice would be really appreciated! Thank you in advance.