good day , I have problem with my iTunes and I can not sync my iPhone XS with my iTunes on my Mac

Connect iPhone to Computer / Mac

Settings > Touch/Face ID & Passcode > USB Accessories > [Enable]

Use your USB lightening cable --> Resolve USB-related alerts in iTunes - Apple Support

If unable to connect --> If iTunes doesn't recognize your iPhone, iPad, or iPod - Apple Support

For your Mac --> If your computer doesn't recognize your iPhone, iPad, or iPod ...

Use genuine cable --> Identify counterfeit or uncertified Lightning connector accessories ...

See how to --> Sync your iPhone, iPad, or iPod using iTunes on your computer ...

If you are experiencing an issue not listed here, contact support

You don't use iTunes in Catalina for a backup

https://www.macworld.com/article/3410567/how-you-back-up-your-iphone-and-ipad-in-macos-10-15-catalina.html