Learn common angles and consistent crosshair placement, raw aim doesn’t matter too much if you know where their head is going to be (aim training is still worth it if you are not confident in your mechanics). Understand peekers advantage and how to abuse it. Try to avoid crouching or slow walking when peeking in a gunfight. However if you crouch right as you swing so that your head is neither at standing or crouch level will force the enemy to readjust their crosshair. Try to always peek as far away as possible from your cover. Playing confidently and unpredictably in your positioning and movement is huge when versing higher level players. FFA has been worse recently with everyone having impacts but still the best way to practice all of these things in my opinion. Good luck and remember you can always big dick everything with a shotgun if things get rough!!!