Watch PVP tricks and tips on YouTube for Minecraft, it helps a lot.
Play with your sensitivity, determine which is easier for you to shoot and aim with.
Strafe a lot. Strafe means to move left and right a lot while fighting, so your opponent finds it hard to hit you.
Finally block hit, lots of players don't block hit but it helps a lot when fighting, you can fight and take half damage at the same time, block hitting and using the rod helps enormously.
Good luck with getting your PVP on!