What should I expect from my first training session?

I‘ve been going to the gym for 5 years now. I was pretty deep into bodybuilding (men‘s physique) but I don’t like the lifestyle anymore so I slimmed down a bit and changed my training routine.

But next to my gym is a JiuJitsu gym. I‘ve been thinking for months to go there and I finally booked my first session (introduction) there.

I‘m super hyped for it. But what should I expect?

Don’t get me wrong, I only mentioned that I go the gym to say that I‘m relatively fit, I don’t expect that this will help me somehow to be good in it and I fully expect to get humbled. I would be ignorant to think that going to the gym helps.

I used to do (english) boxing, but that’s it, so I don’t have any experience.

I‘m quite old now - 27 - is that too late to start?

And will the people be welcoming? How will the first sessions look like?

Thanks!