Transfer my iPhone content to a new iTunes account
My iPhone backup is linked to my partners iTunes account. I am buying a new iPhone and want to set up a new iTunes account for myself but transfer all of my current iPhones content relating to my partners iTunes account to my own new personal iTunes. Please could anyone tell me how I can do this without loosing my current iPhone's app's, photo's, contacts etc?
iPhone 6, iOS 10.2.1