Slow firewall pass through network LAN speed ( <99 Mbit/s) after change ISP to 900 Mbit/s ADSL line

On my shorewall firewall 5.1.10.2 on Centos 7 up to date I have change
ADSL providers from 30 Mbit/s to 900 Mbit/s

On the shorewall server with all network adapter 1Gb with speedtest-cli
I get the real speed (near 900 Mbit/s), but all PC and Notebook with 1
Gb nic adapter on LAN that pass through the firewall, get a slow speed
test (<90 Mbit/s).

I have also try to connect a Notebook direct to server LAN network
adapter to bypass the switch but none is change, speed is <9x,00
Mbit/s.

Insted if I connect the same Notebook direct to router the speed test
go to 900 Mbit/s  

Seem that the firewall pass through limited the traffic speed to 100
Mbit/s

Someone can suggest me what I can check in order to resolve this issue?

Many thanks to All

-- 
Dario Lesca
(inviato dal mio Linux Fedora 35 Workstation)