data collection with rshiny - How can I show each plot separately?

Participants of a study should give an estimation to each plot with an Input Slider.
(to clarify; the output = the plot shouldnt be a function of that input slider)
My goal is to show each plot separately.
The current code doesn't allow it. It shows all plots at once. The second plot should appear after the user has clicked on "next task" and so on. There are more than 3 plots - It's just an example number.

I'd like to save the results in a file, for example like this:
Person 1: plot1 90 plot2 50 plot3 60
Person 2: plot1 40 plot2 60 plot3 40
Person 3...
Person 4...
This file shouldn't appear on the UI.

Can anyone help? This is my main-question above.

((I've also got additional little questions if someones knows it.
I'd also like to show the plots for each participant in a random order. Could I use sample() somehow? Is it also possible to see which order each person had then?))

ps:
I've found out that the following: "stackoverflow.com/questions/38302682/…" might be helpful but I haven't been able to transfer it.

thank you!