How in the hell do people use these planes? I mean when you fight against people they always slow down and then use a lot of maneuvers to dodge you. Using boom and zoom doesn't work for me because they either get behind you or somebody kills them.
The P-38 in a dive builds up a ton of energy. You should be able to comfortably pull away from your target without them having a chance to fire back. Do not try to slow down and turn with someone.
If you dive, miss, you can pull up into a vertical climb and use the camera to see if the person is turning to follow or not. If they aren't, roll back over and dive on them again. If they are, just keep up your climb. They'll be out of gun range pretty quickly if they were in it in the first place.
You need to be climbing at the start of a round, by the way. Climb high enough and nobody will be shooting at you. You'll be perched above the 'furball' of other players slugging it out and you can choose the most advantageous target. If there are six enemies, and five of them are headed in one direction, get the one guy who is by himself.
Keep your energy "up". That means turning speed into altitude whenever possible. A BnZ plane is dead in the water on the deck with no energy. Almost the entirety of the German tree plays this way. The Americans have capable brawlers in the Wildcats, Hellcat, and all of the Cobras. But for the most part, they do even better if you BnZ with them.
The P-38 is a preview of the P-47 aka one of the best planes in the game at its BR. BnZ fighters really benefit from getting all the engine mods, and the P-47 is a total pig before it gets injection. So hang in there.