Implement using Private endpoint

Hi,
I tried to implement the solution in my environment, but I must use a private endpoint to all the public resources: Web app, cosmos db, and a key vault.
When I configured the private endpoints, I received a 500 network error code, and in the "Application log", I received the error attached.
can you please explain how to use the solution using private endpoints?
and, why do we need all the "outbound addresses"? what is there use? can we disable it and how?

Thanks