How to install Nagios on Debian 11.3

Nagios is an open-source monitoring system for computers. It runs on Linux and can monitor devices that are running Linux, Windows, and UNIX operating systems. The Nagios software checks critical parameters of application, network, and server resources periodically.
For more explanation on this video: https://www.linuxhelp.com/how-to-install-nagios-on-debian-11-3