I literally have the same problem. I usually get anywhere between 12-14 out of the first 15 correct, and afterwards, I find myself thinking I might as well just guess the answer choices. I can usually narrow down the correct answer choice to one of 3 possible options. And I always seem to choose the wrong one. I saw some success with skipping 15-20 and doing the last 5 but sometimes I've also seen success doing 15-20.