Thank you for your Answer. I imagined that a feature can have a huge impact on installs.
To your steps: I agree that quality and a great product has to be a requirement. And for step 2 you will have to keep your eyes open.
I am living in Germany and I think that either way you will have good opportunities if you really develop a strong skill set in that field. But if you "hate" frontend" work and are frequently bored in web dev I would say that customers and contractors are often looking for a "complete package" for developing smaller short-term projects.
729 divided by 27 equals 27.
That is why if you tap "=" its still displaying 27 and if you tap it again it divides by 27 and a 1 is displayed.
So the Calculator is working fine.
I think he got a good point and if you are talking in person you can see the reaction to your product "live" and really capture the experience of your tester.
P.S.: Keep up your good work!