How do I improve?

I'm 95% new to this game, not even familiar with the team-based third-person-shooter genre. I only played this game once with a friend group.

I messed up a lot. Took people's weapons by mistake, did nothing because I froze up, couldn't do stims or summon stratogems fast enough, I didn't know what to do at all.

Now they want to play with me again, and I'm worried of messing up again...so what are some things I can do to help get better at the game?

Is there a training room/mode or a way to better learn the controls (I play on nintendo switch controller)? What are the best weapons, stratogems, or anything to help someone like me? What are some tips? I'm open to any advice.

Edit: thank you so much for all the tips and advice. The friend group I'm in understands that I'm still new, they just wanted to dick around by throwing me into super helldive difficulty as a newbie! But they were still helpful and it was still fun, even if I was nervous and messed up a lot. I played the tutorial repeatedly, so I got the controls downpat, mostly. A few more times might do the trick. I got a few hours until I play with them again, so I'll look through the stratagems and weapons and do a few solo missions. Then when I play with them, I'll ask what job I can do, so that way I'll be more useful. As for my anxiety, it's because they're a new friend group and I just don't wanna be an ass or embarrass myself, but that's a me problem that I'm working on. They like me well enough to want me to play with them again, so at least there's that. Again, thanks so much!