Don't try to learn 100% of what you know about a language from an app; and if you can manage to install an input method for your target language, toggle those "rearrange these words" exercises into typing exercises.
If your target language has any media you enjoy watching (this is hard for me with Mandarin, and to some extent Japanese, since I find most of the TV shows basically unwatchable), consume that with subtitles, and pay a bit of attention at first to how things are said. If you hear a new word or phrase which sounds useful by its translation, repeatedly transcribe the phrase in the target writing system, and get a feel for why it means what it does.
Duolingo is a tool, but just as you should not attempt to build a house with only a carpenter's hammer, you should not attempt to learn a language with only Duolingo.
If your target language has any media you enjoy watching (this is hard for me with Mandarin, and to some extent Japanese, since I find most of the TV shows basically unwatchable), consume that with subtitles, and pay a bit of attention at first to how things are said. If you hear a new word or phrase which sounds useful by its translation, repeatedly transcribe the phrase in the target writing system, and get a feel for why it means what it does.
Duolingo is a tool, but just as you should not attempt to build a house with only a carpenter's hammer, you should not attempt to learn a language with only Duolingo.