add popup at moment of redirect to other file

Hello, with click on a button i redirect to first file of my IOS app, however i want display a popup then but that's not working, check my code below here, can someone fix it?

let shopViewController = self.storyboard?.instantiateViewController(withIdentifier: "Tab2")
UIApplication.shared.keyWindow?.rootViewController = shopViewController

displayMyAlertMessage(userMessage: "Uw reservatie is geboekt! Uw heeft een bevestingsemail ontvangen; check ook je spam folder.")