how much to study each day in order to fully understand c++?

Answer 1

As with a new musical instrument or other thing only study as much as your seat (rear end) or mind can absorb. Stop before getting too frustrated and take a break, maybe even till the next day.

As for "fully understand" I suppose you mean to really know it well and that is a lifelong journey as things change over time so use it as much as you can to try to solve problems and having a goal like that will help solidify the thinking and code.

Answer 2

24 hours :)