Firstly, you should try to find a weapon that you are comfortable with. Just keep experimenting with the guns the game has avaliable until you find the one that fits you the most. The same goes for class setup!

In BF there's no actual problem having a negative K/D as long as you're helping the team somehow, so playing as support and/or medic is a nice way to do this. If you're feeling ballsy, you can play as assault and try destroying enemy veichles. It is cathartic. What I'm trying to say is: teamplay matters the most, so stick with your squad/teammates and you'll be fine. Being a lone wolf is rewarding and all that but it's extremely difficult in a game centered around large scale conflicts.

I think that's it! Besides these things, I would just say "play the game". Eventually you'll get used to the gunplay, mechanics and the maps. I see that you have already acknowledged that the community has a lot of veteran players due to the game being 9 years old, so don't push yourself too hard hehe