Run Unity in background on mobile platform

I know it is a question already been asked but the answers that I found are 4 years old at least. I have an app (iOS and Android) that run a timer (handled with Time.deltaTime) when I "hide" the app by going on the home or reduce the app in any other way the whole app stops. I'd like to know if there's a way to run the Update in background or if there's a more elegant solution to my problem. EDIT: What I am trying to do is to run a timer, my game is a quiz game in which you have to answer within 10 seconds. So in background the timer should run normally and if it passes the time it should set the answer as wrong and go on the next question.