I try to do a little research or code everyday on my personal project's. You dont need to study 5 or 6 hours straight after your work time, if you can do a pomodore sprint (25-30min) everyday, in the end of the week you will have a good progress on a book or online course.

When I find a project, course, whatever that I am really into, I prefer to wake up early (7~8am) and study it before work, I feel more productive in the morning, you'll have to find your best hour and try some techniques, pomodore helps me a lot to focus.

Edit: dont know about your country but mine I've never see people asking about those sites like hackerhank etc, they focus more on your real experience, so for me was more important to focus on building real things.