Macos – Why are the apps in “/System/Volumes/Data/Applications” and “/Applications” the same in macOS Catalina

see here ;) https://emacs.stackexchange.com/questions/53026/how-to-restore-file-system-access-in-macos-catalina you will find solution. Clic on MAC preference / security / Privacy / and check all boxes

To do this you must temporarily disable some of the system's best protections against malware, so to play it safe, first make sure your machine is free of malware, disconnected from any network, and that you have a good (tested) full-system backup.

Next, disable System Integrity Protection:

1. Reboot in Recovery Mode by holding down ⌘+R at boot.
2. Once you are fully in Recovery Mode, run Terminal by selecting it from the Utilities menu in the menubar.
3. In Terminal, enter csrutil disable.
4. Reboot back into a normal boot.

Once you have disabled System Integrity Protection and rebooted, you can remount the boot volume read-write with this command:

sudo mount -uw /

Now you can make the desired changes.

Finally, Don't Forget! Re-enable System Integrity Protection:

1. Reboot in Recovery Mode by holding down ⌘+R at boot.
2. Once you are fully in Recovery Mode, run Terminal by selecting it from the Utilities menu in the menubar.
3. In Terminal, enter csrutil enable.
4. Reboot back into a normal boot.

Note that the sudo mount -uw / is not persistent across reboots, so you don't need to explicitly undo it. The reboots you did to re-enable SIP already caused the root filesystem to get remount read-only again.