If you want my advice here how I will make it if I was you: first create global variable called :"PlayerTime" ,
1- then create condition: "Every 1 second" and "If Player.count=1" ==> add 1 to playerTime.
Once the player is destroyed, the PlayerTime will stop.
2- Add text and set condition: "Everytick" ==> Set text (any name) to ("Time: "&PlayerTime)
Hope it would help you