I am using my own pc to connect to my company VPN what can they see?

Your curiosity regarding connecting to the company VPN what can they see can be answered as - It depends on the VPN used and I have never used Citrix. But AFAIK, VPN solutions commonly configure the network in a way that the machine is seen as local to the remote end of the VPN. That means that once connected to the VPN, all your network exchanges go through the VPN connection. Any other way would open an uncontrolled gateway between the internal network and the global internet.

All corporate VPN solutions I have used were that way: once connected, all network traffic goes through the VPN.

That means that your company should not know what files exist on your computer and for privacy reasons should not even try to know. But if you connect to Netflix once the VPN is on, it is likely that both the requests and responses pass through the VPN and the corporate proxy to the internet. You should control what routes exist on your machine when connected to the VPN to confirm it, normally the command netstat -r can be used to show that. Of course encrypted exchanges should normally not be decodable, but network admin generally abhor netflix requests through their network…