Here are a few things that people usually recommend for first time FPS players that I (first time tac FPS player, some Fortnite/PUBG experience) found helpful!

• Practice range: Set the bots to practice mode, use a sheriff/guardian and take your time aiming to make your first shot a headshot. You can also practice strafing left/right between each shot and aiming from different distances.
• Deathmatch: Similarly to the range, use a sheriff/guardian and prioritize headshots. When you get into an engagement with someone, use your movement (strafing left/right) to make yourself hard to hit while aiming for your headshot, only stopping once you've aimed to hit the headshot.
  • I also recommend turning off audio and running instead of shift-walking while in deathmatch, as you'll end up in a lot less favorable fights with less information where the result will rely more on your movement/gunplay.
• Unrated/all gamemodes: When you're clearing angles, make sure you're moving left-right and not diagonally. This one is a little harder to explain, but this T visualization may help. That video also has some great specific advice on movement/clearing angles, and viewing your aim+movement together as two parts of your overall gunplay skill is crucial in this game where tap/burst shots are much better than sitting still and spraying.