Litetween behaviour may help you in this part
I have used this in my game and made popup
on start of the layout stay popup and their buttons out of screen
when player died or collision with enemy > start (litween position)
when click any button > reverse (litween position)
something like this you can do
popup will go smoothly to out of screen and come in smoothly to
you can do some other thing in this behaviour
like first popup come then after button appear
do experiment and you can do some amazing things