The most effective way of learning a language is still a classic way. Book a language course, with an actual teacher, try to read as much as possible, watch movies, and when you are up to talk, talk, talk, ...
IMHO, no app can help learn a language except as a vocabulary learning helper, in which case something as simple as Anki flashcards app is good enough.
IMHO, no app can help learn a language except as a vocabulary learning helper, in which case something as simple as Anki flashcards app is good enough.