Exercises
All of the questions in this list stem from questions that are actually asked in interviews. You likely won't get these questions exactly, but you'll get questions that touch on the same concepts and exercise the same muscles.
The questions here are tough — I don't expect you to finish, but at least for practice, this high level of difficulty is intentional. You should work through all parts while practicing, because you're training to be in that top 1% that can breeze through these parts.
Granted, some of these questions may be way too hard, but I'd rather err on the side of too-hard than too-easy. Since there's no repository of interview questions online, these are the questions you practice and learn backwards from.
Given that, don't worry about how quickly or how slowly you're going. Focus on the high level takeaways, so that you're ready when you hear a similar concept in a real interview.