I would like to learn a new language after I have mastered Spanish, I already know Chinese, English and is learning Spanish. What language should I learn next? Maybe French? Thanks!
German. It is widely spoken, there are lots of people on Duolingo to help, and its not too similar to Spanish that you will get confused. It is a little harder but I would say the next up on a scale of the difficulty of languages.
Alternatively, you could try German's easier but less spoken cousin, Dutch.