problem with test result

Hello i am no expert but i tried to improve my websitespeed.
on test 11 of march all A besides CDN which we do not use. After some changes now we have first Byte time F and Caching D, F, C depending on when running test. other speedtesting Tools like pingdom Show good results and improved Situation. but webpagest this bad results. Google pagespeed also Shows good 90. Can someone help me here what goes wrong maybe? here you see the test history:
the last very good one was 11.march. after got worse