In learning about troubleshooting network congestion, i need with identifying metrics that can be used to determine issues with network congestion or bottlenecking of data on a network. then in your own (easiest to understand/beginner level) words, identify how these metrics can be used to diagnosis and resolve network congestion.

So you need to know key metrics that can be used to troubleshoot your network. You can see real-time values of network performance, like Network Bytes Received/Sent per second, by using Windows Resource Monitor. You can open it in Windows Task Manager (Ctrl+Alt+Del) in Performance tab. Click "Open Resource Monitor" and go to "Network" tab. I guess it will be helpful for beginner.

First I would ping the server you have trouble communicating with. 
Second, I would run a traceroute the command is tracert server-name this will give you an idea on where the bottle neck might be,
Third I would check the error logs in both WS and Server. 
Fourth I would check logs on the switches/routers if any. (you might need to enable logging for a short period of time since it takes a big hit on performance.
Use Microsofts Network Monitor and see if you see any abnormalities. 

Same issue happened to me i had 4/5 and suddenly they went down to 3/5 .the reason must be that the question u recived a brainliest answer mark, was deleted by a moderator. they can delete a question for some reason if it isn't complete or has been reported. so there for that is most likely the reason.best of hope u earn another one

Answer use the open or open file command in the file menu.