I'm using duolingo too to learn Japanese. Once you get the hang out of reading the hiragana and katakana it's not that bad to learn it. The Kanji is a different story. I'm trying to learn Japanese for multiple reasons:
1. I would like to visit Japan one day, and not the touristic cities but travel through the countryside.
2. I want to be able to understand Japanese spoken anime without needing subs and to be able to read the little jokes/details that are sometimes hidden in the scenes.
I already speak Dutch, English and, if I brush up on it a bit, French. German is a different story, I can somewhat read enough to understand the basics and if they speak slowly enough I can understand it too, but I can not write or speak it myself. I never had any German at school. Maybe, in the far future, when I can speak Japanese well enough I might try and learn German too with Duolingo. I just don't want to confuse my brain now with 2 languages, learning them is hard for me too. I have a science brain, not a language brain