Ok here's a step-by-step guide
1.) Grind your aim and movement over and over and over again. It needs to be second nature to you, so you can do it without thinking. Your brain needs to be focusing on more important things. If you're ever thinking consciously about your aim or movement in a game, you simply haven't practised enough.
For doing this outside matches, I prefer DM. Or if not then MGE against soldier / demo. Scout v scout MGE is mostly useless, because in 95% of teamfights if you ever spam ADAD you'll just get a rocket to the feet.
Once you can aim and move well without thinking, you can move on to step 2.
2.) Actively start thinking and practising about your positioning. As everyone knows, high ground = good. The winger is broken because it lets you almost instantly take the high ground on every point of every map, but most scouts don't use it to its full potential.
When your team loses an (even) team fight, it's often because your scouts got bullied off the high ground, or never managed to take it in the first place.
Of course, positioning is also highly dependent on the current uber situation, how many people are alive for each team, etc. Should you be holding close? Holding back? Hiding? Moving forward? Retreating?
Again, once you've been thinking actively about your positioning for a while, you will be able to do it without thinking too much about it. Move on to the next step.
3.) Actively think about and practise your target prioritisation in team fights. This is probably the hardest skill to master, because it depends on so many different factors. It's also why b4nny is the best scout in the world despite his aim not being amazing.
You don't want to just be braindead shooting whoever is closest to you, yet most scouts do exactly that. You need to focus fire down targets with your team. This is actually most important for the scout in particular because hitscan is near-guaranteed (just don't miss LOL) to kill a low health enemy. You are the "clean up" class, so you need to do your job.
Someone on your team (probably the demo or the pocket scout) should be calling the main focus target in team fights, and others can chime in if and when they get an enemy low.
Obviously there are exceptions to this. Sometimes shooting the bombing soldier instead of your team's current focus target is best. Like I said, it's highly situational. Mostly it comes from experience, but you can actively improve it by watching your own gameplay (streaming or local recording is great because it's important to hear what your team was calling at the time).
I also recommend you watch b4nny scout pov on his stream, and pay special attention to how he positions himself in team fights and how he chooses who to shoot.
Once you're DMing on autopilot, you'll have a lot more "brainpower" available in game to actively think about your positioning. Once you get positioning on autopilot too, you'll be able to actively listen to your team and decide who you should be shooting at. Once you get a feel for all that, you'll also start to understand the game on a higher level. You'll have overall become a much better and more consistent player.
But all that is kinda hard work so maybe just play DM more idk lol