The ISP is the local telephone company - via fiber optic.
A “fast switch” is just an ethernet switch faster than those of some years ago. This one is more common than mine:
https://www.amazon.com/gp/product/B000BC7QMM/ref=ox_sc_act_title_1?smid=AWXBONHVNQ00F
Supposedly there is a firewall in the fiber-optic interface unit from the ISP, but, it’s possible I misunderstood that. Every computer but my desktop feeds from some sort of router (the PowerLink is essentially a form of router.)
First, gigabit switch ports are the baseline standard these days. It was considered fast when I got my first one perhaps 15 years ago.
2.5GbE is coming on, and really 10GbE and better is what all the cool kids are doing in their homelabs.
Generally fiber connects to an ONT, an optical network termination that converts the FO to a twisted pair Ethernet jack of an appropriate speed (1, 2.5, 10). That typically goes on to a router, or the ISP might provide an all in one ONT/router/network switch. Maybe even include a WAP, wireless access point.
It’s unclear to me which of these functions are being handled by your ISP gear, and what by something else.
If your ISP provides the router, you might see if there’s a management interface you can log into and see status of things and change setting if need be.