By the way, for our other friends who care about the matter of "Qickly <> Fastest" I'll say that it'll be so difficult to prove that with English except if you are an expert in English. Many times clarifying the differences between similar English words by English itself will be an obscure work, that you'll reach to a no so good clear meanings, or you lack kind of Arabization of the meanings, and it's - according to my experience in English - some difficult in English itself for some essential attributes of English itself that it's not so free language in its ways of expressing like Arabic.
It doesn't really take an expert and, if you are interested in mastering English then you should be interested in the differences between such words.
Fastest implies a comparison. It means that in a given set of elements, there is one that is faster than all other elements in the set. For instance, in the set of 100m runners, the fastest ever is Usain Bolt who set the current record.
The people he competed against were obviously very quick and fast (much faster than the average person), therefore it is accurate to say they are quick but, none of them are the fastest, that distinction, so far, can only be used to describe Usain Bolt.
In general terms, Quick is something that happens in less than the average time (for whatever is being measured). Fastest means there is nothing quicker (in the set of course, light is faster than Mr. Usain Bolt, but that is a different set.) So far, if you believe Einstein, light is the fastest of any element in the set of elements that move.
Hopefully, that makes the difference between quick and fast clear. This is a quick explanation but, it certainly hasn't been the fastest one.