The way you do that is through a process called "Heuristic Analysis".
This is a very specific way of looking at your store and applying a set of investigative techniques to evaluate everything on each and every page of your store.
If you do it correctly, you will wind up with an extensive list of problem areas on your store. (HINT: if your list is small, you did it wrong. Our average list is 10 to 15 pages long)
It's not rocket science and there are courses available that you can buy to teach you how to do this.
But it is something that must be learned and like anything that takes time.
As an example, we train all of our staff internally and on average it takes a new data scientist 90 days to become proficient enough with Heuristic Analysis to correctly diagnose a store's issues and basic leakage points.
Now, before you freak out, please read on...
I realize that 90 days of study, on top of everything else you have to do to run your business is probably not attractive to you.
For some people though it is, and I believe in being transparent...so if someone wants to go learn Heuristic Analysis and do it themselves...they can.
But, for you, and anyone else looking to get results NOW, not in 90 days, there is a faster option available to you...