Does everyone's daily goal add up even though you are doing a different language. I want to do three tasks a day, on three languages which I am working on. Is this a bug or does Duolingo just not realise that I've changed language?
Daily goal applies to your time and experience spent on Duolingo, across all of your languages. There isn't a setting to have individual daily goals for individual languages.
It should register towards your XP from each language towards your daily goal. Your daily goal is currently set up at 50 XP, so remember that you need to do at least 5 lessons and not 3 tasks.