I think the "You use this app if you have 5 minutes to kill" is a genius marketing strategy and highly suggest you use this on the website.. it would add a lot of clarity.
I was afraid that the description and the screenshots are not explanatory enough, but it seems you pretty much got it.
Do you have any suggestions on what can I change for people to understand the app better?
You can use it to read short-stories, watch interesting videos, learn facts and basic phrases for ten languages or play some simple games.
You use this app if you have 5 minutes to kill.
I'm working on an explanatory video of the app right now.