You can uninstall iis completely, and then reinstall it, about how to uninstall iis completely you can remove the following roles:
Web Server (IIS) under tab "Server Roles" in Server Manager
And Windows Process Activation Service in "Features" tab in Server Manager
Attention: A server restart is necessary after the uninstallation.
Then delete the files or rename the folder (preferred) for C:\inetpub
and C:\Windows\System32\inetsrv.
Here the key step is to uninstall Windows Process Activation Service (WAS). This is the service responsible for managing application pool configuration, creating and managing lifetime of worker process for HTTP and other protocols. Once WAS uninstalled, we can safely remove the configuration files located under C:\Windows\System32\inetsrv to finally make a clean uninstallation of IIS.
To reinstall IIS, just to follow the same steps: add Web Server (IIS) as well as WAS.
More information about how to perform a clean reinstallation of IIS you can refer to this link: How to perform a clean reinstallation of IIS