How much time a day

So I was wondering what people recommended amount of time a day I should do I’m in year 12 (if you live in England you’ll know what that means ) and Ive just started my a level content unfortunately my school doesn’t teach Greek so I’m out to learn it myself but I was wondering if anyone studying or still in school had a like time recommendation for now I’ve just been doing the alphabet on Duolingo which has helped but I was just wondering!