Safari and AppStore aren't working after macOS Big Sur update

lisam95 wrote:

since I updated to big sur, safari or app store dose not working anymore. I also have trouble accessing other apps. Why is that?

You do not paint a very big picture...

—Reboot

—Try a SafeBoot https://support.apple.com/en-us/HT201262

Takes noticeable longer to get to the login screen, does a 5-15 minute disk repair before it fully boots up, and certain system caches get cleared and rebuilt, including dynamic loader cache, etc.

Login and test. Reboot as normal and test as caches get rebuilt.

—How to reinstall macOS from macOS Recovery - https://support.apple.com/en-us/HT204904

I was afraid of that.

There is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac.  This user tip describes what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community.  

Download and run Etrecheck. Etrecheck is a diagnostic tool that was developed by one of the most respected users here in the ASC and recommended by Apple Support  to provide a snapshot of the system and help identify the more obvious culprits that can adversely affect a Mac's performance.

IMPORTANT:

Before running Etrecheck assign Full Disk Access to Etrecheck in the Etrecheck's Privacy preference pane so that it can get additional information from the Console and log files for the report:

Also click and read the About info to further permit full disk access.

Copy the report

and use the Additional Text button to include the report in your reply.

Then we can examine the report and see if we can determine what might be causing the problem.

Writing an effective Apple Support Communities question

Have you installed or run any "cleaning", "optimizing", "speed-up" or anti-virus apps on your Mac?

Strongly suggest following the advise of @ Old Toad. Really knows his stuff and very trusted.