C_THR91_1811 practice tests are different in the way that these tests are simulated. The questions are in exact number and the time i got to attempt the similar SAP SF Onboarding certification exam questions was 180 minutes which is what i get in actual exam. So i had to learn to attempt the questions in the stipulated time and also make sure that the attempts are correct. This was something that i learnt only on erpprep.com.