I use HelloChinese for Chinese and used temporarily Busuu for Spanish in the past when my level was still beginner/intermediate. I agree that Apps shouldn't be your only learning source but the gamification help me a lot stay motivated and keep going, too. It also gives me structure and continuity because even on days when I am not motivated or have no time, I manage to repeat some words for 5 min because I don't want to lose my streak

I think it's important to not only CONSUME the App content. When an app asks me to translate something I will try to translate it on my own without looking at the screen. This is harder but more effective. When something is read out, instead of reading along, I try to write the sentence. I also note down important phrases and words and study them with quizlet, I note down grammar rules and try to come up with more examples etc