I just played my second game and I have no idea wtf I'm supposed to be doing. Is there no way to play against bots just to get an idea of how the maps work? Do I just keep doing my best?

I just got my first agent unlock and I don't know who to get. Should I get whatever agent interests me or also account for skill? I am horrible at shooters. I've played other shooters in the past but I always sucked at them. The only one I...