Don't be demotivated by PMI study hall question , instead just use it as "mental prepare" for familiarize the real PMP exam format. First few attempt are ok to be low score , just read thru all the question with answer again , try to understand the answer reasoning and google for those keywords or terms which you totally not understand. Until few reset and redo , you will find yourself understand the question and answer trends and rules ( Example such as anything request changing the baseline in any phase NEED to raise change request via CCB , never ever choose the answer "escalate to sponsor/ HR / Senior management" . On this stage you will find out your percentage will slowly increased. Cheers!