Is helpful to learn languages all week 7 days a week?
Well, if you care about your LingQ streak (the number by the apple) then it does have to be every day. In general more time is better, and studying regularly is good because you will probably spend more time in total.
Better 15 minutes every day than 2 hours once a week
Generally yes, though sometimes it is better to take day off rather than try to force yourself into studying when you don’t want to. But when you do take a break make sure that you will go back to language learning next day. I don’t even remember how many times I wanted to have a day or two of laziness, and ended with few months…
The answer is - yes. And not only one time, but several times a day.
What’s next - 24 hrs a day?
the “Fluent in 3 weeks”, plan. Guaranteed to work!
Yes, you should learn in the 7 days a week because it needs continuity and practice it daily. If you are not practicing it daily you will not be able to learn it by the time and you need more time to learn than others.