Hi zanyra,
Welcome to the Apple Support Community. I do apologize for the inconvience that you are having with your iOS 14 Beta. If you are having an issue with your iPhone, you can report it to Feedback Assistant which is in your App Library or your screen. It is recommended that you do a backup with iCloud or iTunes (Finder in Catlina). After you back up the device, it is recommended that you Restore the device and create a clean install of iOS 13.5.1. If iTunes/Finder gives you an issue while restoring, you can also try using Apple Configurator 2 Beta. This worked when I had an issue with my XR. After that, when you go though setup, you can select Restore from iCloud or Restore from iTunes/Finder. In this post I am including a links to Apple Support articles which might help you out.
Backing up your Device
How to back up your iPhone, iPad, and iPod touch - Apple Support
Recovery Mode
If you can't update or restore your iPhone, iPad, or iPod touch - Apple Support
How to restore from backup
Restore your iPhone, iPad, or iPod touch from a backup - Apple Support
Best of Luck
-Apple_Tekh