Make sure you’ve got the scoped sens right. 38 relative sens is as close to 1:1 as we can get in Overwatch. The rest is down to crosshair placement and practice.
Ana bot training isn’t helpful as she has one of the weirdest hitboxes in the game. Do some widow HS only lobbies to practice instead, or grind out deathmatch to improve your aim.(That’s what I do at least, hope it was helpful.)