Hello Helpmeapple9018,
Thank you for using Apple Support Communities! I understand that you're unable to download or purchase apps after updating your iPhone 11 to iOS 13. I can understand how important it is that you're able to download and use the apps you need to, and would be happy to help.
I'd like to start by having you follow the suggested troubleshooting steps in the following support article:
If you can’t download or update apps on your iPhone or other Apple device - Apple Support
If you're still experiencing the issue after, could you tell us more specifically what's happening when you try to download or purchase an app? If you encounter an error, what does it say? Can you update apps?
Cheers!