I used to live by a gondola downhill park in the mountains and I rented a big squishy downhill bike a few times and did a day riding.
These were really steep technical trails where you have to ride the brakes or quickly build a lot of speed and the bike and the trail wants you to be in the air often.
It's fun sure, put I found it pretty stressful too.
Hard to get in the zone. Having confidence is one thing, but what it feeds into is really feeling it while you're riding. You're totally alert but also relaxed. Being able to find that feeling while doing something probably just comes down to familiarity. If you rode your mtb and these trails with your freinds more and more you might find that feeling.
But for me, it's backcountry XC (crosscountry) riding, gravel riding, and road riding. That's where I can get in the zone. Effort puts my mind there more than Adrenalin. And there's still fun to be had. The caveat here is that doing gravel or xc riding on an excessively competent bike, like you have, makes it boring.
'training' on easy trails/ roads with your bike won't really build any of the skills you lack and it won't be much fun either. I would suggest you try, once all this calamity blows over, to find/buy/restore an old cheaper -but good- bike to ride, maybe a rigid 90s mtb, which will actually challenge your skills on even easier trails, but with much lower stakes. That practice will translate much better when you go riding technical trails with your friends.
Which is, despite all i've said, very fun.