How to collect statistics about VPN connections?

There is a bunch of Mikrotik + Windows Radius (NPS) + AD. How can I handle statistics on VPN connections in some visual form? Mikrotik writes logs, I collect them in mikrotik syslog daemon, I filter by the line “logged in | out” but I just can not find how to process them later.
At the moment, I summarize the time of the sessions later in Excel, but this is inconvenient.
The task is simple - I need to get the total time that a person spent with VPN enabled. There can be several reconnects, you need a total amount per day.
Tell me, please, the simplest solution.
thanks

I would use RADIUS accounting to collect such statistics.

I use Network Policy Server Role as Radius and I have the opportunity to collect logs from the radius, but I can’t find a simple solution for my tasks, just connect a huge and heavy billing. Is there any simple solution to working with these logs?

How does your RADIUS server stores the accounting information? Is there an option to store it in a relational DB? You would then be able to use simple SQL queries for aggregation and reporting.

Yes there is. I was looking for a ready-made version (script or PHP-request, or report generator), maybe someone did this. Because writing is not very difficult, but for a long time for me.