How do you make a compelling app that earns you a little on the side?

#appdevelopment

I created these apps in order to make a few buck on the side:

https://play.google.com/store/apps/details?id=de.pandaquests.reflex
https://play.google.com/store/apps/details?id=de.pandaquests.reflextester2
https://play.google.com/store/apps/details?id=com.ionicframework.vnpronoun2794112
https://play.google.com/store/apps/details?id=de.pandaquests.whenwillidie
https://play.google.com/store/apps/details?id=de.pandaquests.todo

But in total (you heard it right: not individually but in total) they make each month only a few cents. Some months even no revenue whatsoever. The apps have been on the store for several months already. And nothing has changed so far. I want to make at least $1 each month (I want to start small).

Can you tell me why and should I improve on? I'm eager to learn and improve. I'm open to any criticism. In fact I'd be very grateful for that. Thanks in advance.