Are you expecting us to actually download this app to our Android devices in order to give you feedback? If so, I think you will be disappointed. Several of us only operate on Apple devices so if you haven't done an iOS version, we can't use it. Many others will be very reluctant to download something they know nothing about. You need to find a way for us to have a play with it on our computers without downloading/installing anything.
I've had a look at the few screens that are available via that link. I don't know why the slides which read "Study teaches you what you need to know to pass the quiz" seems to have a capital "P" on "pass" and a capital "Q" on "quiz". Neither is necessary.
In another slide, it reads "Quiz tests your Phrasal verb ability, you must pass the quiz to unlock the next stage. There should be no capital letter on "phrasal". The comma should be a full stop or a dash. If you choose a full stop then "you" must start with a capital letter.