You've been at it 3 weeks and you still haven't been taught the form? Have you at least worked on the basics in isolation?
I have to agree with Mook. That is a bit concerning. Usually, Sil Lim Tao is the first thing you start off with. It's essential for building a solid foundation. You don't normally get into full blown chisao for quite some time -- certainly not before having learned the first form.
Well, yes. It's customary to teach some of the basics such as stance, punching, foot-work, and maybe something like pak-sau sometimes before Siu Nim Tao. All of that is part of Siu Nim Tao anyway. But I've never heard of jumping into full-blown Chisao without covering the form first.
The best thing to do to improve reflexes and speed is to literally give it time. Get used to the movements and perform them correctly. If you rush with speed you will end up fast but with bad technique and structure. You take your time, and take it slowly since you've only been doing Wing Chun for a matter of weeks, you will eventually have good speed and technique. I had to do things slowly for a few months.
