Skype for Business Server 2019 Troubleshootin

I've recently upgraded from Lync Server 2013 to Skype for Business Server 2019 and moved all the users to the new pool.

A few users complained that they face issues while having an audio/video conference call and when they share the document via desktop sharing, it takes time to load it on other people's screen. I've setup monitoring and currently working on deploying Call Quality Dashboard (CQD). I will setup very soon.

To begin troubleshooting and narrow down the issue to Network, Client Machine or Server Configuration I need some tips where to begin and pinpoint.

I was not able to copy paste my entire question... please refer screenshot attached.