Thanks for visiting the Apple Support Communities and asking for help with your iPhone and backing up to iCloud, and a second question about the connection to your car. I am happy to check these out with you.
For the backup problems, please try the troubleshooting provided in this help article: If iCloud Backup couldn't be completed or you can't restore
For your USB connection to your car, this help article has troubleshooting for you to try: Get help connecting your iPhone, iPad, or iPod touch with your car stereo
There are many good troubleshooting steps provided. Since you did not mention which iOS version your device is using or if this used to work before an update, there is also a step included to help you check if the car stereo needs an update to work with your device or the newer iOS version which states:
6. Check your car’s manual for help. You might need to install firmware updates for your stereo.
If you still have issues, please let us know what you are experiencing, and the exact alert or error codes received. Thanks again and have a great rest of your day.