You are sure you have complete and valid information because you can download and check out the Koran yourself and verify the author of the preface of this antique Koran once owned by the second president of the US John Adams is right when he says "... thou shalt find in this book [a multitude of incongruous pieces], and divers repetitions of the same things."
Whether the first part of this statement (a multitude of incongruous pieces) is true or not is unimportant. This website is not about theological content, it is about the effect of reciting these texts. You do not have to read the entire Koran, a couple of pages is enough to see the pattern. On this website the pattern is illustrated by coloring three themes identified by the author. Whether the website author is correct in selecting these three themes or not again is not the issue. You can decide on what exactly are "the same things" that are repeated yourself.
Muslims recite the Koran; this too is a fact you can easily verify. They (the Muslims) tell us so and you can find websites of Koran schools on the internet.
It follows you have complete and correct information and you can't be manipulated by withholding information, clever arguments, the assertion you misunderstand because you are not an expert and so forth.