Nextcloud version : 20.0.4
Operating system and version : NextCloudPi 1.34.7
The issue you are facing:
Update current instance to a new Nextcloud version
Nextcloud Updater
[X] Check for expected files
The following extra files have been found:
Does anyone know a solution to the problem? I am relatively new to the topic Nextcloud
hey @galaxyrun and welcome to the user-forums of nextcloud.
the answer to your question… well you might find it several dozen times here on the forum as it was asked quite a lot. so next time please feel free to search the forum first before opening a new thread 
in short: you can move that file out of your NC-directory, then try to update again and then move it back to the directory you found it. that’s the safest way. (btw: remember doing backups before you start updating and juggling around with things) .
the easiest way would be: just remove it (but I dunno where this file comes from and if you’d need it urgently)
that did the job. Thank you! 