Unable to open with Iphone 4

Iphone 4 oldugu icin mi bilmiyorum fakat acamiyorum umarim sorunu cozersiniz.
I dont know if because of my cellphones model is Iphone 4 or not but I can not get access to the application. It is not even opening.

The guy with the Iphone4 about Freeletics: Workouts & Fitness, v3.3.1