Translating simple math explanations into GRE math questions

Does anyone else have a problem with translating what you learn in the math guide into useful information on the Practice problems.
For example, I have covered Integers, Primes, Factors, and Multiples.

However, for example:
if n = 20! + 17 than n is divisible by which of the following? 15, 17, or 19? I have no idea how learning about the above topics prepares me to answer this question at all. I had no idea how to even start solving the problem until Greg explained at which point I was like “ok that’s super easy, but how was I supposed to know to do that based on what I have learned thus far”

another example is the following:
if n is a positive integer and the product of all integers from 1 to n, inclusive, is a multiple of 999 what is the least possible value of n…

once Greg explains it in the video it makes sense, but I have no idea how I am supposed to arrive at that with just the basics of the above-mentioned topics.

Am I just too early in the process and missing certain topics or what?

@user211 It just happens with practice buddy.

Just like riding a bicycle, you learn to ride it on straight road first and then start taking it to school through traffic. Then after a few weeks when you get comfortable, you plan to go on bicycle on a steep slope with your mates. You might fall, but then you get up and get a hold of you bicycle and then ready to ride it anywhere.

Similarly, just practice, maybe start from solving basic questions instead of jumping. You might be just jumping to harder questions.

n = 20! + 17 → this is a gmat level question and it is also there on gmat club website, with pretty low successful solve rate.

Relax, just keep at it, you’d be able to solve them in no time.