Adyen Interview Question

First interview - Some Adyen formula questions. Hackerrank: - LC easy-medium end java question - Completing some java classes that need to pass tests (Their tests have really low coverage so you don't need to fill classes all but some, which they expect vice-versa but in terms of Hackerrank you got %100 score :D) - 3 SQL questions that was almost all easy Hackerrank solutions interview: - Why did you do that? - How could you improve?