If I understand you correctly, you want users hitting the external link to be directed to the internal.
This is usually handled by a DNS service.
In pfSense if you are using the DNS Resolver, a host override should suffice.
Services -> DNS Resolver -> General Settings -> Host Overrides -> Add
Host: testcompany
Domain: sytes.net
IP Address: 192.168.88.88
Description: my site override
Save
Apply
Test
Of course this will redirect not only that page, site, http, but any request to that host incl https and any other protocol trying to hit that host name.