Can’t open file on desktop

Does the same issue present while booted in to Safe Mode This does a repair Disk, clears cache files and only loads Apple Software, extensions and Fonts. So, loads slowly which is normal Once logged in the computer will look and preform differently - also normal. Run in this mode for as long as it takes to Test your exiting issue. Should the problem not present in Safe Mode - there might be either a User Account issue or some third party software interfering with the normal operation of the OS.

As @ Luis S has suggested download the application

Suggest downloading the Application Etrecheck directly from a Trusted Developer and well Respected ASC Contributor. The application is free or paid from added features. Run the application with Full Disc Access ( Security & Privacy - Full Disc Access ). It will take a Snap Shot -  both the hardware and software. The Report will Not Reveal Any Personal Information. Post back the Full Report - copy and paste - using the Additional Text Icon ( 3rd Icon to last )

We can have a look at the report for possible issues and may have possible suggestions to resolve the issues.

Any Third Party Applications that will interfere with the normal operation of the OS, alter, modify, remove or delete or attempt to do so is an invitation for disaster and may require a Reinstallation of the OS.

Initial review as per below. The list is very extensive including running outdated version of Big Sur 11.2.2.

Shall away further input from @ Luis S - but if this was my computer - which it is not - would Wipe the Drive 100% Clean and reinstall afresh. Would Not use Time Machine Backup to Migrate anything else but the User Account. Install only needed and supported Big Sur Compatible applications and never install Antivirus of other Security Software.

StoreJet Transcend 1

macOS Big Sur 11.2.2 (20D80) 

Unsigned Files:

  Launchd: ~/Library/LaunchAgents/homebrew.mxcl.mongodb-community.plist

    Executable: /usr/local/opt/mongodb-community/bin/mongod --config /usr/local/etc/mongod.conf

    Details: Domain name invalid - possibly adware

  Launchd: ~/Library/LaunchAgents/com.node.HIPKILocalServer.cht.plist

    Executable: /bin/zsh -c ~/Library/HiPKILocalSignServer/runHIPKILocalServer.sh

    Details: Domain name invalid - possibly adware

PulseSecureFirewallSysExt - version 1.0 (Pulse Secure LLC - 2020-10-16)

    Application: /Applications/Pulse Secure.app - version 9.1.9 (Pulse Secure LLC - 2021-07-11)

Kernel Extensions:

  /Applications/Pulse Secure.app

    [Not Loaded] PulseSecureFirewall.kext - net.pulsesecure.PulseSecureFirewall (9.1.9 - SDK 10.13)

 [Loaded] org.macosforge.xquartz.startx.plist (Apple Inc. - XQuartz - installed 2016-10-26)

 /Applications/AppCleaner.app/Contents/Library/LoginItems/AppCleaner SmartDelete.app

We need more information. Please run Etrecheck and post its full report here.

Use the “additional text” button and paste the report into the text box.