How to export multiple JIRA Issues into a JSON-file with JIRA REST API?

[Jakob Holzinger]

Hey I want to export all Issues assigned to a user in a JSON file to import and use it elsewhere. My API-Call is like this: 

$"{url}/rest/api/2/search?jql=assignee={userId}"

 How do I get the result of the call into a proper formatted JSON file?

I am coding in C#

Thanks for your help!