[mindcrime]

Why would learning BJJ help in sales?

It probably wouldn't. But that isn't the question here. Look at what the OP wrote:

I'm shy and I feel weird talking to people, looking into their eyes. Talking to a group of people will make my voice shaking and I feel inferior and less confident whenever I talk to people

That isn't a sales problem, that's a basic, fundamental issue of confidence, self-assurance, "frame of mind", or whatever you want to call it. If you can't even look at people and talk to them, you're not "doing sales" yet.

What weight-lifting and jiu-jitsu can help with, in my (admittedly anecdotal) experience, is that "confidence, self-assurance, etc." stuff. The stuff that's a prerequisite before even getting to the actual sales part.

[bigred100]

Since I don’t live in a dangerous area or work as an MMA fighter that stuff wouldn’t help me. Frankly my opinion of what’s scary about people is self-centeredness, social connections, whether they have willingness to throw me under the bus for their benefit, etc. No help from jiu-jitsu unless it makes them bond with you. Or maybe a (my opinion) small but noticeable positive benefit looking athletic can give you.