So if you have lets say a 2:45 which is 165 seconds. you wanna be sub 2:30. What you can do is you look at the run above you thats at least a second better then your run. observe the run and summarize what the did to get that time. once you do that, you can try to execute the improvements. If you already have the wr, you can still do this, just see what mistakes you made in the run and try to fix them in future runs one mistake at a time. I hope this is helpful and hopefully you progress faster with this method. :)