I wish to read Kant's Critique of Pure Reason in the near future, but I have read that it is better to read the Critique in its original German. However, I don't know German. I have read the works of Friedrich Nietzsche and Max Weber in translation, and I understood their ideas well. Is it much better to read Kant's Critique of Pure Reason in German, and if so, why?
It depends. The main thing is, that some English translations do not render properly the Kantian jargon, and thus, they need to explicitly tell you what they mean with a certain term. This can get ambiguous and usually the term is instead, more often than not, translated via more difficult English terms, or even via sentences instead of single terms. The same problem happens when you translate Kant to Italian; it becomes much more difficult than it is in German.
Keep in mind that Kant still is difficult, especially to a non-native speaker, but the benefit that you get from reading any philosophical text in the original language is worth learning the language itself. The best example is reading translations of Aristoteles. The translations are not bad in themselves (Kantian slip?), but in this precise case, if you take any two translations of the, say, Metaphysics, they will seem totally different texts.
Getting to a conclusion. Should you invest in learning German to read Kant? Well, again, it depends. Are you really interested in German philosophy? If yes, you should definitely learn some German. Nietzsche in the original is a bliss. But if you are not highly motivated and you do not have quite a good amount of time on your hands, I would rather look for really good translations.
As stated in the comments, I should have emphasized more the fact that reaching that level of understanding of the German language requires time and effort. Since Kant is difficult even for the majority of native speakers to understand (as I can quite safely induce from my experience), do not expect to be able to read, for example, the CPR after one year of German lessons. Some scholars have been known to learn a language in a month. You might know about Toshihiko Izutsu, who apparently learned classical Arabic in a month to read the Quran in the original. However, these are remarkable exceptions; thus, please be conscious of the level of German you are going to need to not misread any philosophical text in this language.
I heartly suggest checking out the two links regarding the Nietzschean terminology added to this question by Stephie, it gives a rough idea about what to expect.