I am new at this also. According to your graphic it looks like you are trying to make a 90degree turn backwards. There are videos that teach you to swoop in and out method and your trailer will look like you had already made the turn forwards. I'm confused too. The back end of the trailer should be close to a 45degree angle to the corner,. See video for clarification. I look at my rear axle wheel and remember that is the pivot point.
Good Luck. https://www.youtube.com/watch?v=RLtfrBWzNCw
PS after less than 20 times I now can park it like a pro truck driver.