PowerBI Report Server

Hi, 

I have power bi report server and i need to know how much time users spent on reports. 

For example, i need to know how much time is report session is open and how much time users spend on watching reports. 

I have a ReportServer database, but i only have a logs for steps, i dont know how to find for example : 

I open report at 10:50:30s and watching to 10:55:00s, setting filters and etc, and after that i close my window with report, and i would to know that I spent 4 minutes and 30 seconds on watching report. 

How I can solve this problem?

Anybody have solution?

Thank you