network bridge and subnet

RouterOS Beginner Basics
1

Hello
'I have a wan network from my ISP (192.168.2.1) and I do not want to create a subnet so I configured it as bridge ether1; 192.168.2.4/24 with gateway 192.168.2.1. The problem is that computers should route through 192.168.2.4 so that the firewall works fine. but I want my devices route through the 192.168.2.1 and listen to the firewall. What can I do?

Thanks

mariog