Becoming a translator

I want to become an interpreter. Fluent Forever suggest to use the flashcards with one side having the word in the language we are learning (Japanese) and in the other side to have a picture. If I want to become an interpreter, do you recommend from the beginning to have one side of the flashcard to have Japanese and the other the translation? o is it better to become fluent in Japanese first? If the second is true then how do you work in your translation ability from Japanese to English?  Thanks!