I'm about to sit for the test and I found this app called "Prepare Remote Pilot." I don't have any stake in this at all. You tube has a lot of stuff but this app has:
Regulations 73 questions
National Airspace System 80 questions
Weather 66 questions
Loading and Performance 28 questions
Operations 67 questions
It comes with charts and figures attached to each question along with an explanation of every question and answer. It only costs $4.99
I've been doing a lot of studying and thought I was ready but this app made it clear that I am not. Just FYI. Hope it is helpful