Probably, you have to backup the phone and reset the phone.
For apps, you can try to use Helium app https://play.google.com/store/apps/details?id=com.koushikdutta.backup&hl=en
For SMS and call log, you can find apps in Play store.
For photos, you can back them up to Google+ (with Photos app)
Contacts, gmails are always synced with your Google account. Backup is not necessary.
For other downloaded files, manually copy them to your PC.