How to design a foreign language learning app?

Question

Java

It is necessary to design an application for learning a foreign language (no matter what).
The application must fulfill the following requirements:
1. There must be a dictionary.
2. There must be the possibility of training words.
3. Words can be distributed according to the frequency of use.
The essence of the question: how can all this be implemented?

Answer 1

To the answerer above:
Use for some time the best application in your opinion and write down all the shortcomings. And then repeat without these shortcomings.

Answer 2

You should always start with an analysis of competitors and their products.