Hello Guys, please i need a good network monitoring device or software. my network is in a mess. Is there any better device that i can use as my gateway and firewall instead of Cyberoam, because the cyberoam doesn't filter all site properly. Thanks all.

The truth is there isn't really any one size fit all software that does web content filter perfectly. Cyberroam is probably one of the best out there and it still messes things up.
There are scripts out there that work with specific equipment/hardware, but still have issues.
Web content filtering is complicated in that it distorts functional services that make your network run smoothly, especially DNS request services.
Entering filter rules based on input/output traffic on your gateway instantly affects how data is routed in and out of your network.
An insight into your network topology and running config is a great way to start troubleshooting

You could check out squid. It's a web caching and proxy server software.